Intrusion prevention system
||It has been suggested that Intrusion detection system be merged into this article. (Discuss) Proposed since April 2013.|
Intrusion prevention systems (IPS), also known as intrusion detection and prevention systems (IDPS), are network security appliances that monitor network and/or system activities for malicious activity. The main functions of intrusion prevention systems are to identify malicious activity, log information about this activity, attempt to block/stop it, and report it. 
Intrusion prevention systems are considered extensions of intrusion detection systems because they both monitor network traffic and/or system activities for malicious activity. The main differences are, unlike intrusion detection systems, intrusion prevention systems are placed in-line and are able to actively prevent/block intrusions that are detected.  More specifically, IPS can take such actions as sending an alarm, dropping the malicious packets, resetting the connection and/or blocking the traffic from the offending IP address.  An IPS can also correct Cyclic Redundancy Check (CRC) errors, unfragment packet streams, prevent TCP sequencing issues, and clean up unwanted transport and network layer options.  
Network-based intrusion prevention system (NIPS): monitors the entire network for suspicious traffic by analyzing protocol activity.
Wireless intrusion prevention systems (WIPS): monitor a wireless network for suspicious traffic by analyzing wireless networking protocols.
Network behavior analysis (NBA): examines network traffic to identify threats that generate unusual traffic flows, such as distributed denial of service (DDoS) attacks, certain forms of malware and policy violations.
Host-based intrusion prevention system (HIPS): an installed software package which monitors a single host for suspicious activity by analyzing events occurring within that host.
Detection methods 
Signature-Based Detection: This method of detection utilizes signatures, which are attack patterns that are preconfigured and predetermined. A signature-based intrusion prevention system monitors the network traffic for matches to these signatures. Once a match is found the intrusion prevention system takes the appropriate action. Signatures can be exploit-based or vulnerability-based. Exploit-based signatures analyze patterns appearing in exploits being protected against, while vulnerability-based signatures analyze vulnerabilities in a program, its execution, and conditions needed to exploit said vulnerability.
Statistical anomaly-based detection: This method of detection baselines performance of average network traffic conditions. After a baseline is created, the system intermittently samples network traffic, using statistical analysis to compare the sample to the set baseline. If the activity is outside the baseline parameters, the intrusion prevention system takes the appropriate action. The particular intrusion in this case monitors users and network behaviors.
Stateful Protocol Analysis Detection: This method identifies deviations of protocol states by comparing observed events with “predetermined profiles of generally accepted definitions of benign activity.”
See also 
- Intrusion Detection System (IDS)
- Denial-of-service attack
- Host-based intrusion detection (HIDS)
- Network intrusion detection system
- Real-time adaptive security
- Bypass switch
- "NIST – Guide to Intrusion Detection and Prevention Systems (IDPS)". 2007-02. Retrieved 2010-06-25.
- Robert C. Newman (19 February 2009). Computer Security: Protecting Digital Resources. Jones & Bartlett Learning. pp. 273–. ISBN 978-0-7637-5994-0. Retrieved 25 June 2010.
- Michael E. Whitman; Herbert J. Mattord (2009). Principles of Information Security. Cengage Learning EMEA. pp. 289–. ISBN 978-1-4239-0177-8. Retrieved 25 June 2010.
- Tim Boyles (2010). CCNA Security Study Guide: Exam 640-553. John Wiley and Sons. pp. 249–. ISBN 978-0-470-52767-2. Retrieved 29 June 2010.
- Harold F. Tipton; Micki Krause (2007). Information Security Management Handbook. CRC Press. pp. 1000–. ISBN 978-1-4200-1358-0. Retrieved 29 June 2010.
- John R. Vacca (2010). Managing Information Security. Syngress. pp. 137–. ISBN 978-1-59749-533-2. Retrieved 29 June 2010.
- Engin Kirda; Somesh Jha; Davide Balzarotti (2009). Recent Advances in Intrusion Detection: 12th International Symposium, RAID 2009, Saint-Malo, France, September 23–25, 2009, Proceedings. Springer. pp. 162–. ISBN 978-3-642-04341-3. Retrieved 29 June 2010.