TLS record layer

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The Structure of TLS

At the bottom is the TLS Record Layer which handles all data transport. The record layer is assumed to sit directly on top of some reliable transport such as TCP. The record layer can carry four kinds of payloads:

  1. Handshake messages.used for algorithm negotiation and key establishment.
  2. ChangeCipherSpec messages.really part of the handshake but technically a separate kind of message.
  3. Alert messages.used to signal that errors have occurred
  4. Application layer data

We focus on describing the record and handshake layers since they are of the most relevance to DTLS.

Record Protocol

The TLS record protocol is a simple framing layer with record format .Each record is separately encrypted and MACed. In order to prevent reordering and replay attacks a sequence number is incorporated into the MAC but is not carried in the record itself. Since records are delivered using a reliable transport, the sequence number of a record can be obtained simply by counting the records seen. Similarly, encryption state

  • ClientHello
  • ServerHello
  • Certi_cate
  • ServerHelloDone
  • ClientKeyExchange
  • [ChangeCipherSpec]
  • Finished
  • [ChangeCipherSpec]
  • Finished
  • TLS handshake

Is chained between records. Thus, a record cannot be independently decrypted if for some reason the previous record is lost.

Handshake Protocol

The TLS handshake is a conventional two round-trip algorithm negotiation and key establishment protocol. For illustration, we show the most common RSA-based variant of the handshake in Figure 2.

A TLS client initiates the handshake by sending the ClientHello message. This message contains the TLS version, a list of algorithms and compression methods that the client will accept and a random nonce used for antireplay.

The server responds with three messages. The Server-Hello contains the server's choice of version and algorithms and a random nonce. The Certi_cate contains the server's certi_cate chain. The ServerHelloDone is simply a marker message to indicate that no other messages are forthcoming. In more complicated handshakes other messages would appear between the Certi_cate and the ServerHelloDone messages. The client then chooses a random PreMasterSecret which will be used as the basis for each side's keying material.

The client encrypts the PreMasterSecret under the server's RSA public key and sends it to the server in the ClientKeyExchange message. The client then sends the ChangeCipherSpec message to indicate that it is changing to the newly negotiated protection suite. Finally, the client sends the Finished message which contains a MAC of the previous handshake messages. Note that the Finished message is encrypted under the new protection suite.

The server responds with its own ChangeCipherSpec and Finished messages.

As with the record layer, the handshake protocol assumes that data is carried over reliable transport. The order of the messages is precisely de_ned and each message depends on previous messages. Any other order is an error and results in protocol failure. In addition, no mechanism is provided for handling message loss. Retransmission in case of loss must be handled by the transport layer.

Internet protocol security(IPsec)

This is the protocol suite for the securing IP communications by authenticating and encoding each IP packet from the data. IPsec also added protocols for establishing common authentication between agents at the starting of the session and negotiation of cryptographic keys to be used throughout the session. IPsec can be used to protect data flows between a pair of hosts, between a pair of security gateways or between a security gateway and a host.

IPsec is a dual mode, end-to-end, security format working at the Internet Layer of the Internet Protocol Suite. This is used more in the internet security system like a Secure Sockets Layer (SSL), Transport Layer Security (TLS) and Secure Shell (SSH), operate in the upper layers of these models. Hence, IPsec can be used for defending any application traffic across the Internet. Applications need not be particularly designed to use IPsec.

Modes of operation

IPsec worked in the host-to-host transport mode, same like in a network tunnel mode.

Transport mode

In this mode, only for the data transfer of the IP packet from data. The data is encrypted or authenticated. The routing is integral, since the IP header is neither modified nor encrypted

When the authentication header is used, the IP addresses cannot be translated, hash value is invalid . The transport and application layers are always secured by hash. this mode is used for host-to-host communications.

Tunnel mode

In tunnel mode, the entire IP packet from the data is encrypted or authenticated. Then data is encapsulated into a new IP packet with a new IP header. This mode is used to create Virtual Private Networks for network-to-network communications. host-to-network communications, and host-to-host communications.

B. TLS and Psec advantage

In the TLS a connection is connected, the client and server communicate with the ciphersuite. With the exchange of ciphersuite codes in the client side hello and server replay with the message hello. Which specifies a combination of cryptographic algorithms. This is used in the connection. The key exchange and authentication algorithm are uses the public key algorithms. The message codes are used the messages authentications and made up from cryptographic hash functions using the HMAC for TLS

IPsec they don't used any ciphersuit and any cipher messages are not used.. In the TLS uses the combinations of cryptographic algorithms. TLS provides supports the more secure two-sided connection mode. In which both ends of the "conversation" can be certain with whom they are communicating. This is known as mutual authentication. The total communication will be done by the certificate verify mode between server and client.

IPsec main advantages this is a protocol suite for the communication. This is also establishing the communication between the end-to-end and also dual mode communication. This also provides the mutual authentication. Actually IPSec suite is a framework . this is uses the following protocol for the different functions

  • Internet key exchange
  • Authentication header
  • Encapsulating security payload

The internet key exchange to create the security association by handling the protocols and algorithms and generate the encryption and authentication keys this is used by IPSec.the second protocol provides the connectionless integrity and data origin authentication for IP datagrams and gives the protecting against replay attacks. The last protocol Encapsulating security payload

provides the confidentiality and the data origin authentication, connectionless integrity.



Internet Group Management Protocol or IGMP ability to allow a switch to "listen in" on network multicasts. The switch then delivers traffic to ports where the attached device signals it's available to listen to the broadcast.

In the above diagram explains the basic stricture of Internet Group Management Protocol. It is related to ICMP for unicast connections. IGMP can be utilized for online streaming video and gaming, and allows more efficient use of resources when supporting these types of applications. IGMP is very weak to some attacks, and firewalls commonly allow the user to halt it if not needed

Simplified Network Management Protocol

An administrator uses simplify Network Management Protocol, or SNMP, to watch and configure systems, switches and other devices. This is important as the number of devices increases, to record and analyze network traffic, notify the network manager of network problems in real time and to speed and simplify corrections.

Web Based Management

The advantage of Ethernet base devices, tools or programs is web access to supervise network operations, configuration and security. Manage switches have this ability, and efficiency and stability are facilitated by remote web access.


The "silver bullet" of security is for only essential communication to flow from end to end a network, when it's wanted and only with devices that need it. Managed switches are an important part of the solution, as they create and manage VLANs, monitor problem traffic through port mirroring, and enable other security related actions.


The AOIM uses spatial, temporal, and functional classes for establishing membership in multicast network groups. Multicast services allow randomly sized groups to communicate on a network through a single transmission by the source. Multicast provides one-to-many and many-to-many delivery services for applications such as teleconferencing and spread imitation in which there is a need to communicate with several other hosts concurrently. In the example, a multicast teleconference allows a host to send voice and video concurrently to a set of locations. With broadcast, data is sent to all hosts while unicast or point-to-point routes communication only between two hosts. The Internet Group Management Protocol (IGMP) provides an addressing method for an unreliable, connectionless, multicast service that is routable over the Internet. From the outlook of the AOIM, IP Multicast allows the making of transient multicast groups that can be associated with an entity's area of interest (AOI). In this background, IP Multicast addresses can fundamentally be used as context labels instead of physical destinations.

B. Protocol-Independent Multicast (PIM)

PIM is a in the part of multicast routing protocols for Internet Protocol networks that gives one-to-many and many-to-many allocation of data over a LAN, or the Internet. It is termed protocol-individual because PIM does not contain its own topology detection mechanism, but as an alternative uses routing information supplied by other conventional routing protocols. PIM provides for both dense and sparse group membership. It is different from other protocols, since it uses an explicit join model for sparse groups. Joining occurs on a shared tree and can switch to a per-source tree. Where bandwidth is plentiful and group membership is dense, overhead can be reduced by flooding data out all links and later pruning exception cases where there are no group members.

There are two modes of operation with this protocol. PIM-DM (dense mode) and PIM-SM (sparse mode).

The main difference between PIM-DM,PIM-SM in two essential ways only i.e.

  1. There are no interrupted joins transmitted, only explicitly triggered prunes and grafts.
  2. There is no RP (Rendezvous Point).

Protocol Independent Multicast

Sparse-Mode is a protocol for proficiently routing IP packets to multicast groups that may span wide area and inter domain internet. The protocol is called as " protocol-independent" because it is not dependent on any scrupulous unicast routing protocol for topology discovery and sparse-mode because it is suitable for groups where a very low percentage of the nodes will give to to the multicast session. Unlike previous dense-mode multicast routing protocols such as DVMRP and dense multicast routing which busy packets everywhere and then pruned off branches where there were no receivers, sparse-mode openly constructs a tree from each sender to the receivers in the multicast group.

Dense mode multicast also one mode that multicast can use to build a tree for sending packets to the multicast subscribers. It is the opposed of sparse multicast. Dense mode is perfect for groups where many of the nodes will subscribe to receive the multicast packets, so that most of the routers must receive and forward these packets. The source originally broadcasts to every router, and thus every node. Then each node that does not wish to take delivery of packets intended for that group will send a prune message to its router. Upon receiving a prune message, the router will modify its state so that it will not advance those packets out that interface. If every interface on a router is pruned, the router will also be pruned.

Task 3


Rube and kibsa systems are connected to the internet with the IP. In the email task involved four hosts. Generality host means two way access to other computer in the internet. In this task ruba and kibsa are two hosts and the mail servers of two kibsa and rube are another two hosts. In the email sending process between two system rube and kibsa involved 4 hosts that is first process starts ruba system. When gives the send command ruba mail id uses the SMTP send to the local mail transfer agent (MTA). In this time run by ruba's ISP( internet service provider)

The mail transfer agent search at the destination address provided in the protocol SMTP, in this case x is internet email address of kibsa. The mail transfer agent (MTA) resolves a domain name to decide the fully qualified domain of the main exchange server in the domain name system.

The DNS severer for the domain, response with any mx records listing the mail exchange servers for that domain in this case a server run by kibsa's ISP. sends the message to using SMTP, which delivers it to the mailbox of the user kibsa. When kibsa presses the getmail button in his MUA, which gets up the message using pop3.


In the email sending process the systems (ruba and kibsa) connected to the internet with the IP (internet protocol) this is used for connects the system and identifies the system in the internet by using the IP address. And in the process of sending email through the SMTP (system mail transfer protocol), SMTP used for transfer the e-mails in the internet between two or more servers. And the receiver kibsa get the mail through the pop3 (post office protocol).


From one system to another system send the file in the internet that uses different type if internet media formats. That is based on the stranded of MIME( multipurpose internet mail extensions). This is define the internet media formats. In the case of assignment provided text message" Please find attached abstract and figure 1" is in the format as a plan text. In the internet that is transfored in the format of "text/plain" as a textual data. And the image in the format of jpeg is in internet "image/jpeg" . the attachment document is in the format of "application/doc" because this is multipurpose files. The data transferred in the email attachments multipart type when the data archives and other objects made of more than one part. The format is "multipart/mixed".

Task 4

IPv4 and IPv6

Internet protocol is some set of technical rules that defines the network computer communication. There are two types of protocol versions IP 4 and IP 6.


This is the first version of IP to be mostly used worldwide. This internet protocol most of today's internet traffic. There are over 4 billion ipv4 addresses. That is a lot of IP addresses. It is not sufficient to future.


This is the new version of internet protocol provides a much more address pool then ipv4. This is deployed in 1999. This is meets the world's IP addressing requirements for future.

Deferments of IPv4 and IPv6

Internet Group Management Protocol (IGMP)

In the IPv4 Internet Group Management Protocol is use by IPv4 routers to locate hosts that want traffic for a exacting multicast group, and use by IPv4 hosts to notify IPv4 routers of presented multicast group viewers.

     In the IPv6 Replaced by Multicast Listener Discovery protocol. Does basically what Internet Group Management Protocol does for IPv4, but uses ICMPv6 by addition a small number of Multicast Listener Discovery -specific ICMPv6 type values.

Internet Protocol header

In the IPv4 Variable size is 20-60 bytes, depending on Internet Protocol preference present.

In the IPv6 Fixed size is 40 bytes. In that not using a Internet Protocol header options. Commonly, the IPv6 header is easier than the IPv4 header.

Internet Protocol header options

In the IPv4 different options that strength accompanies an IP header.

The IPv6 header has no options. Instead, IPv6 insert extra (optional) addition headers. The addition headers are AH and ESP, hop-by-hop, routing, fragment, and destination. Presently, IPv6 supports some addition headers.

IP header protocol byte

In the IPv4 protocol method of the transport layer or packet payload; for E.g., ICMP.

The style of header right away following the IPv6 header. Use the similar values of the IPv4 protocol field. But the structural design effect is to permit a presently define range of after that headers, and is simply absolute. Then the subsequently header force be a transport header, an addition header, or ICMPv6.

IP header Type of Service (TOS) byte

In the IPv4 Using by QoS and make different services to assign a traffic class.

In the IPv6 assigns the IPv6 traffic class, likewise to IPv4. use dissimilar codes. Presently, IPv6 doesn't sustain TOS.

iSeries Navigator support

In the IPv4 iSeries Navigator supply a total pattern answer for TCP/IP.

Similar for IPv6. No CL commands are accessible for IPv6 arrangement.

LAN connection

In the IPv4 use by an IP interface to catch to the physical network. several types exist; for E.g., token ring, and Ethernet. At times referred to because the physical link, or physical interface.

IPv6 be able to be use with any Ethernet adapters and is as well maintain more virtual Ethernet among logical partitions.

Layer 2 Tunnel Protocol (L2TP)

In the IPv4 Layer 2 Tunnel Protocol can be thinking of as virtual PPP, and facility over any sustain line type.

In the IPv6 presently, the i5/OS execution of Layer 2 Tunnel Protocol doesn't support IPv6.

Loopback address

In the IPv4 interface through an Internet Protocol address of 127.*.*.* (typically that preserve only be used by a node to throw packets to itself. The physical interface or line description calling name is LOOPBACK.

In the IPv6 concept is similar as in IPv4. The single Internet Protocol address is 0000:0000:0000:0000:0000:0000:0000:0001 shortened version ::1. The practical physical interface is also calling LOOPBACK.


     In the IPv4 netstat is implementing to appear at the status of TCP/IP links, interfaces, or routes. accessible by iSeries Navigator and 5250.

Similar for IPv6 and IPv6 is sustains for both 5250 and iSeries Navigator

Maximum Transmission Unit (MTU)

In the IPv4 MTU of a link is the highest number of bytes that a exacting link type, such as Ethernet or modem, supports. For IPv4, 576 is default minimum value.

IPv6 have an architected lesser bounce on Maximum Transmission Unit of 1280 bytes. That is, IPv6 force not portion packets under this limit. To send IPv6 more than a link with a smaller than 1280 Maximum Transmission Unit, the link-layer should transparently fragment and defragmenter the IPv6 packets.

Network Address Translation (NAT)

In the IPv4 Network Address Translation is a basic firewall task included into TCP/IP, configured by iSeries Navigator.

In the IPv6 presently, Network Address Translation doesn't support IPv6. More commonly, IPv6 doesn't need Network Address Translation. The extended address space of IPv6 remove the address lack problem and allow easier renumbering.

Network table

In the IPv4 on iSeries Navigator, a configurable tables that connections a network name by an IP address exclusive of mask. For E.g., host Network14 and its Internet Protocal address

In the IPv6 presently, no modify are complete to this table for IPv6.

Node info query

The IPv4 is Does not exist Node info query.

An easy and suitable network tool that must work like ping, apart from with content: an IPv6 node might query an added IPv6 node for the target's DNS name, IPv6 unicast address, or IPv4 address. Presently, not support.

Packet filtering

The IPv4 necessary firewall function included into TCP/IP, configured using iSeries Navigator.

The IPv6 You can not use packet filtering with IPv6.

Packet forwarding

In the IPv4 i5/OS TCP/IP stack preserve be configured to promote Internet Protocol packets it obtain for non-local Internet Protocol addresses. Typically, the inbound interface and outbound interface are linked to separate LANs.

IPv6 packets are not forwarded.

Point-to-Point Protocol (PPP)

In the IPv4 is supports PPP dialup interfaces in excess of various modem and line types.

In the IPv6 presently, the i5/OS implementation of PPP doesn't support IPv6.


In the IPv4 using Ping basic TCP/IP implement to check reach ability. Presented using iSeries Navigator and 5250.

Similar for IPv6, and IPv6 is support, for together 5250 and iSeries Navigator.

Port restrictions

In the IPv4 i5/OS panels permit a client to configure a chosen port number or port number range for TCP or UDP so that they are only on hand for an exact profile.

Similar for IPv6. Port limitations for IPv6 are the similar to those existing in IPv4.


In the IPv4 TCP and UDP have different port spaces, each recognized by port numbers in the range 1-65535.

In the IPv6, ports work the similar as IPv4. Since these are in a new address family, there are now four different port spaces. For E.g., there are two TCP port 80 seats to which an application can bind, one in AF_INET and one in AF_INET6.

Protocol table

In the IPv4 on iSeries Navigator, a configurable table that associates a protocol name with its assigned protocol number; for example, UDP, 17. The system is shipped with a small number of entries: IP, TCP, UDP, ICMP.

The table can be used with IPv6 without change.

Private and public addresses

All IPv4 addresses are public, except for three address ranges that have been designated as private by IETF RFC 1918: 10.*.*.* (10/8), through (172.16/12) , and 192.168.*.* (192.168/16). Private address domains are commonly used within organizations. Private addresses cannot be routed across the Internet.

IPv6 has an analogous concept, but with important differences. Addresses are public or temporary, previously termed anonymous. See RFC 3041. Unlike IPv4 private addresses, temporary addresses can be globally routed. The motivation is also different; IPv6 temporary addresses are meant to shield the identity of a client when it initiates communication (a privacy concern). Temporary addresses have a limited lifetime, and do not contain an interface identifier that is a link (MAC) address. They are generally indistinguishable from public addresses.

IPv6 has the notion of limited address scope using its architected scope

Task 5

A. Intrusion detection system

Intrusion detection system is application that monitors networks and suspicious activity and alerts the system. In some situations the ids may also respond abnormal by taking the actions like blocking the users and IP address from the network.

Intrusion detection system comes in range flavors and approach to detecting doubtful traffic in different ways. That is network based (i.e. called NIDS) and host based (i.e. called HIDS) introduction systems.

Documenting the existing threats to an organization. Intrusion detection enables the collection of information that proves useful in understanding intrusion techniques and the fre- quency and characteristics of the threats to which an organization is exposed and in tailoring the security measures accordingly. Deterring individuals from violating security policies. Being aware that their activity is being monitored, individuals might be less prone to violate the organization's policies out of fear of being detected.

Network Based Intrusion Detection

Network-based intrusion detection systems use raw network packets as the data source. A network-based IDS typically utilizes a network adapter running in promiscuous mode to monitor and analyze all traffic in real-time as it travels across the network. Its attack recognition module uses four common techniques to recognize an attack signature:

  • Pattern, expression or bytecode matching,
  • Frequency or threshold crossing
  • Correlation of lesser events
  • Statistical anomaly detection

Once an attack has been detected, the IDS' response module provides a variety of options to notify, alert and take action in response to the attack. These responses vary by product, but usually involve administrator notification, connection termination and/or session recording for forensic analysis and evidence collection.

The example of NIDS is snort

     Snort is a free open source programming. It capable of identify attacks and study packet logging and real time traffic analysis on the network. More features snort is protocol analysis, content searching/matching, and is usually used to keenly block or passively detect a variety of attacks and probes,

Host based intrusion detection system

   Host Intrusion Detection Systems are typically organize on a host computer. In its place of watch a network sector, a HIDS only watch the host on which it is set up. A HIDS would normally be located on business serious hosts and on servers in a DMZ so as to be the majority likely to be cooperation. The HIDS work by watching modify to a number of variables on the host system.

The example of HIDS is OSSES

  OSSES is a free open source host based intrusion detection programming. It performs operations like log analysis, integrity checking, Windows registry monitoring, time-based alerting and active response. OSSES provides intrusion detection system in most operating systems, like a Linux, Mac OS X, Solaris and Windows. It has a centralized, cross-platform architecture allowing multiple systems to be easily monitored and managed.

B. Strengths and Weaknesses of IDS

Strengths of Network-Based Intrusion Detection Systems

Network-based IDS contain much strength that cannot simply be offered by host-based intrusion detection only. So many network managers (or) many customers deploy network-based intrusion detection when using IDS for the first time due the low cost of ownership and rapid response times. The following are the major critical component of security policy implementation of network based IDS.

Lowers cost of ownership

Network-based intrusion detection allow strategic deployment at critical access points for studying the network traffic intended to multiple systems. These systems do not require loading software and managed on a selection of hosts. Since few detection points are required, the cost of implementing the system very less in enterprise environment.

Detects attacks that host-based systems miss

Network-based intrusion detection systems study all packet headers for signs of malicious and doubtful activity. In the host-based IDS do not examine packet headers, so they cannot identify these types of attacks.

For example in many IP-based DOS (denial of service and fragmented packet attacks can only be recognized by examine at the packet headers as they travel in the network.This type of attacks can be easily identified by a network- based intrusion detection system study at packet stream in real-time.

More difficult for an attacker to remove evidence

In the network-based intrusion detection systems use live network traffic for real-time attack detection. An attacker cannot remove the evidence from the network. The system grab the data includes not only the method of attack, but also the information of lead to help the attack for prosecution.

Real-time detection and response

Network-based IDS detects malicious and doubtful attacks as they occur, and so provide quicker warning and response.

Operating system independence

Network-based intrusion detection systems are not dependent on OS as detection sources for the evaluation.

Strengths of Host-Based Intrusion Detection Systems

     The host-based intrusion detection systems are not fast in the network counterpart, this system not gives the advantages like the network-based systems. The advantages cannot match in both the intrusion detection systems. This system strength includes stronger forensic analysis.

Checking on success or failure of an attack

Host-based intrusion detection systems use logs contain events that have actually occurred. They can evaluate whether an attack was successful or not with greater accuracy and fewer false positives can network-based systems.

Monitors specific system activities

This host-based IDS monitor all the activates like user and file transfer in the network, with file accesses, modifications to file permissions, and monitors install new executables.

Identify attacks that network-based systems fail

Host-based systems can identify attacks that cannot be identified by network-based products. For example, attacks from the keyboard or (any hardware devises) of a server do not cross the network, and so cannot be identified by a network-based intrusion detection system.

Suitable for encrypted and switched environments

This Host-based system survives in on various hosts all through an enterprise. They can conquer some of the deployment challenges faced by network-based IDS in switched and encrypted environments. In the Host-based intrusion detection gives larger visibility in a switched environment by residing on as many critical hosts as needed.

Real-time detection and response

Even if host-based intrusion detection does not present true real-time response, it can come very close if implemented correctly. Not like older systems, this is uses a process to verify the status and data of log files at predefined intervals, so many of host-based systems receive an interrupt command from the OS when there is a new log file entry. This entry must be processed immediately, this is dropping the time between attack detection and response.

Not requires additional hardware

For this Host-based ID system not requires any hardware devises for execute. Host based IDS reside on existing network infrastructure, including file servers, Web servers, and other shared resources. This efficient can make host-based intrusion detection systems very cost effective. These systems do not need any box on the network that requires addressing and maintenance, management.

Lower cost of entry

Comparing with the network based systems host based systems is very lower cost. The system implemented in hundred dollars only.

Weaknesses with the IDS

The following are the weakness of the IDS. The major three weaknesses are false positives, false negatives, and spoofing.

Some IDS are Signature based IDS runs in one mode that is the binary mode. It either identify malicious packet or not. The second type is decisions are based on "I saw an attack" and "I didn't see any attack". Based on this IDS suffers from the problems below.

False Positives

False positives are proceedings that come out to be harmful, in the same way not that harmful. Change IDS to reduce false positives takes more time like months, and no intrusion detection system can gets zero false positives. In the real time scan out of the 100% of warnings that an IDS detects, more than 70% alerts will be false positives.

False Negatives

False negatives are also main drawback of IDS. Some events are undetected by intrusion detection systems because of "did not see any match". We take examples is hexadecimal encoding code of HTTP requests in the network


Is encoded like


Nothing in the rules file "/cm%69-b%69m/" The attack will pass or ignored. Just as suppressing false positives requires time and knowledge, because of this reason more logs from perimeter devices like routers and also application server need to analyzed the network traffic.

Spoofing Attacks

The attacks cannot identify the source IP is valid. IP belong to the same network the attacker used that IPs resides. These attacks ignore by the local traffic in this situation attacker wins.

C. The advantages and disadvantages of IDS

For the most part, IDS's currently come in two varieties:

  • Network Intrusion Detection System (NIDS)
  • Host Intrusion Detection System (HIDS)

The techniques that also the NIDS or HIDS uses to decide if malicious action is happening can be based ahead recognized signatures or anomalies touching normal model of activity. Which technique an exacting IDS uses depends leading the dealer and manufactured goods. The next is a brief clarification of the 2 main IDS categories.

Network Intrusion Detection Systems

Network Intrusion Detection Systems are typically organize as a devoted element on a network division. There is some dispute as to where to put a single NIDS (inside or outside of a firewall), but mainly have the same opinion that many NIDS are improved. It will then evaluate capture network data to a file of identified malicious signatures. If there is a competition, the IDS will log and drive an alert according to how it was configured by the system or security administrator.

Some of the advantages and disadvantages of NIDS are:


  • Avoid DoS that would otherwise affect a Host
  • Breadth of Coverage. An entire subnet may be covered by one NIDS.
  • Stealth
  • Minimal Install/Upgrade Impact to Network
  • Ability to Identify Network Layer Errors
  • Operating Environment Independent


  • Latency between time of attack and time of alert. By the time an alert is received the damage may have already occurred.
  • False / Positive Alerts
  • Cannot Analyze Encrypted Traffic
  • NIDS only as strong as the latest signature update. New or variations in attack patterns will not register.
  • Difficulty in processing packets in a congested network.
  • Does not indicate whether the attack was successful

Host Intrusion Detection Systems

Host Intrusion Detection Systems are typically organize on a host computer. In its place of watch a network sector, a HIDS only watch the host on which it is set up. A HIDS would normally be located on business serious hosts and on servers in a DMZ so as to be the majority likely to be cooperation. The HIDS work by watching modify to a number of variables on the host system.

This may include:

  • System Processes
  • Registry Entries
  • CPU Usage
  • File Access and Integrity Checking
  • and many other variables.2

Any surpass doorsill or distrustful file modify will send an alert.

Some of the advantages and disadvantages of HIDS are:


  • Ability to provide information about a host during an attack on that host.
  • Ability to associate a user to an event
  • May detect attacks that are not detectable by NIDS
  • Can analyze encrypted data that has been decrypted on the host.


  • HIDS are not able to detect network scans.
  • Information provided by the HIDS becomes unreliable as soon as an attack on that host has been successful.
  • When an OS is brought down by an attack, the HIDS goes down with the system.
  • In order to monitor several hosts, an HIDS would need to be placed on each host.
  • HIDS may be ineffective during a DoS attack
  • HIDS require resources of the host in order to operate.

Every one type of IDS has its strengths and weaknesses. A top perform is to make use of a selection of explanation and put them keen on strategic region all through your infrastructure. Now that we contain taken a look at the present IDS machinery, we will now start on to discover what tomorrow will carry in the meadow of IDS technology.