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Intrusion Detection
• Detection and protection from attacks against networks
• Three types of network attacks– Reconnaissance– Access– Denial of service
2Engineering and Management of Secure Computer Networks
Intrusion detection system (IDS)
• An Intrusion detection system (IDS) is software or hardware designed to monitor, analyze and respond to events occurring in a computer system or network for signs of possible incidents of violation in security policies.
– These incidents of violations can be unwanted attempts to access, manipulate or disable computer systems, mainly via a network, such as the Internet.
3Engineering and Management of Secure Computer Networks
Classification of Intrusion Detection
• Profile or Anomaly based intrusion detection– Monitors network traffic and compares it against an
established baseline for normal use• Bandwidth, protocols, ports and devices generally connecting
to each other– Alerts the administrator or user when traffic is
detected which is anomalous, or significantly different, than the baseline.
– Example: Snort Spade plug-in– Prone to high number of false-positives
4Engineering and Management of Secure Computer Networks
Classification of Intrusion Detection
• Signature based intrusion detection– Also known as Misuse Detection
• A signature based IDS will monitor packets on the network and compare them against a database of signatures or attributes from known malicious threats.
• Similar to the way most antivirus software detects malware.
– Examples: Cisco Sensors 4200 series, Snort– Less prone to false positives – Unable to detect zero-day threats whose signatures
are not available
5Engineering and Management of Secure Computer Networks
Types of Intrusion Detection Systems
• Host based intrusion detection Systems– Software (Agents) installed on computers to monitor input
and output packets from device– It performs log analysis, file integrity checking, policy
monitoring, rootkit detection, real-time alerting and active response.
– Examples: • Cisco Security Agent (CSA) , OSSEC, Tripwire
6Engineering and Management of Secure Computer Networks
Firewall
Corporatenetwork
Agent
Untrustednetwork
Agent Agent Agent
Agent Agent
DNS serverWWW server
Agent Agent
Host-Based Intrusion Detection
7Engineering and Management of Secure Computer Networks
Types of Intrusion Detection Systems
• Network-Based Intrusion Detection Systems– Connected to network segments to monitor, analyze and
respond to network traffic.– A single IDS sensor can monitor many hosts– NIDS sensors are available in two formats
• Appliance: It consists of specialized hardware sensor and its dedicated software. The hardware consists of specialized NIC’s, processors and hard disks to efficiently capture traffic and perform analysis.
– Examples: Cisco IDS 4200 series, IBM Real Secure Network• Software: Sensor software installed on server and placed in
network to monitor network traffic.– Examples: Snort, Bro, Untangle
8Engineering and Management of Secure Computer Networks
Corporatenetwork
DNSserver
WWWserver
SensorSensor
FirewallUntrustednetwork
Network-Based Intrusion Detection
Management System
9Engineering and Management of Secure Computer Networks
Sensor Appliance Interfaces
Monitoring Interface
Command andControl Interface
ProtectedNetwork
Management System
Sensor
Switch
Router
Router
Untrusted Network
10Engineering and Management of Secure Computer Networks
Promiscuous-Mode Protection: IDS
A network device sends copiesof packets to the sensor for analysis.
If the traffic matches a signature,the signature fires.
The sensor can send an alarmto a management console andtake a response action such asresetting the connection.
TargetManagement System
Sensor
2
23
1
Switch
Switched Port Analyzer (SPAN)
11Engineering and Management of Secure Computer Networks
Inline-Mode Protection: IPS
TargetManagement System
The sensor resides in thedata forwarding path.
If a packet triggers asignature, it can bedropped before itreaches its target.
An alert can besent to themanagement console.
Sensor
12Engineering and Management of Secure Computer Networks
IDS and IPS Deployment Considerations
– Deploy an IDS sensor in areas where you cannot deploy an inline device or where you do not plan to use deny actions.
– Deploy an IPS sensor in those areas where you need and plan to use deny actions.
13Engineering and Management of Secure Computer Networks
IDS and IPS Deployment Comparison
Attacker
Inside
Sensor on Outside:• Sees all traffic destined for
your network• Has high probability of raising
false alarms (false positives)• Does not detect internal
attacks
Sensor on Inside:• Sees only traffic permitted
by firewall• Has lower probability of false
alarms (false positives)• Requires immediate
response to alarms
Internet
14Engineering and Management of Secure Computer Networks
CorporateNetwork
Network based IDS and IPS Deployment
ManagementServer
IPS Sensor
Firewall RouterSwitchSwitch
UntrustedNetwork
DNSServer
WWWServer
DMZ
SwitchIDS Sensor
15Engineering and Management of Secure Computer Networks
IDS and IPS deployment example in an Enterprise Network
Branch
ManagementServer
Sensor
FirewallRouter
NM-CIDS
CorporateNetwork
UntrustedNetwork
DNSServer
WWWServer
Sensor
DMZ
Agent Agent
16Engineering and Management of Secure Computer Networks
Perf
orm
ance
(Mbp
s)
Network Media
Cisco IDS Family
IDSM-2
IDS 4255
IPS 4240
45
600
80
250
200
IPS 4215
10/100/1000 TX
NM-CIDS
10/100 TX
AIP-SSM
10/100/1000 TX 1000 SX 10/100/1000 TX Switched/100010/100/1000 TX
Snort
• Open source, freely available software except for rules• Installed as dedicated server on Windows and Linux,
Solaris operating systems• Placed as network sensor in a network• Rules are set of instructions defined to take certain
action after matching some sort of signatures (atomic or composite)• Example:
• alert tcp $HOME_NET any -> $EXTERNAL_NET any (content:"uk.youtube.com”;msg:"someone visited YouTube";)
18Engineering and Management of Secure Computer Networks
Snort Modes
• Sniffer Mode• Used to sniff traffic from network• Traffic will be captured using libpcap or winpcap.• Traffic will be captured directly from the sensor .
• Logger Mode• Simple logging into a file. Two possible formats are Binary and ASCII.• Logging into a Database (eg. MySQL)• Can be used for creating the normal traffic profile
• Intrusion Detection / Prevention• The rules will be used in this mode of snort to detect unwanted activity
19Engineering and Management of Secure Computer Networks
IDS/IPS Vulnerabilities
• Cisco IPS Packet Handling DoS - • In July 2006, a DoS vulnerability was discovered on Cisco
IPS 4200 series models which were running version 5.1 software.
• Snort Rule Matching Backtrack DoS - • Snort versions 1.8 through 2.6 had a DoS vulnerability ,
found on January 11, 2007 which can exploit Snort's rule matching algorithm by using a crafted packet. This could cause the algorithm to slow down to the point where detection may become unavailable. Snort was quick to release version 2.6.1 which corrected this issue.
20Engineering and Management of Secure Computer Networks
How to protect IDS?
• Don't run any service on your IDS sensor.
• The platform on which you are running IDS should be patched with the latest releases from your vendor.
• Configure the IDS machine so that it does not respond to ping (ICMP Echo-type) packets.
• User accounts should not be created except those that are absolutely necessary.
21Engineering and Management of Secure Computer Networks
Unified Threat Management (UTM)• Unified Threat Management (UTM) is a
network device that have many features in one box, including:– IDS, IPS, Firewall, Spyware, Anti Spam , Anti
Phishing – Anti Virus, Content (www) Filter, VPN
– Example: Untangle, Watchguard– Untangle Demo:
http://www.untangle.com/video_overview/
22Engineering and Management of Secure Computer Networks
Summary• Intrusion detection system (IDS) is software or hardware designed to
monitor, analyze and respond to network traffic .– Can be classified as Profile or Signature based intrusion detection.
• Signatures can be defined as Atomic or Composite.– Can be available as Host or Network based Intrusion detection .– IDS is used as promiscuous mode protection in DMZ– IPS is used as Inline mode protection for securing internal network – Cisco 4200 series IDS and IPS sensors offer rich set of features for ISD
and IPS– Snort is an open source, free IDS and can operate in sniff , logging and
Intrusion detection/prevention modes. Snort uses rules to analyze traffic.
– IDS/IPS software can be vulnerable to exploits so run patched version, and shutdown unnecessary services.
• Unified Threat Management (UTM) is a network device that have many features in one box. E.g, Untangle, Watchguard.
Engineering and Management of Secure Computer Networks 23