Intrusion prevention system
An intrusion prevention system (a computer security term) is any device which exercises access control to protect computers from exploitation. "Intrusion prevention" technology is considered by some to be an extension of intrusion detection (IDS) technology, but it is actually another form of access control, like an application layer firewall. The latest Next Generation Firewalls leverage their existing deep packet inspection engine by sharing this functionality with an Intrusion-prevention system. The term "Intrusion Prevention System" was reportedly coined by Andrew Plato who was a technical writer and consultant for NetworkICE.
Intrusion prevention systems (IPS) were invented in the late 1990s to resolve ambiguities in passive network monitoring by placing detection systems in-line. A considerable improvement upon firewall technologies, IPS make access control decisions based on application content, rather than IP address or ports as traditional firewalls had done. As IPS systems were originally a literal extension of intrusion detection systems, they continue to be related.
The first commercial IPS was the BlackICE product from NetworkICE Corporation. It provided host and in-line network IPS capabilities using protocol analysis as its core detection technique. The first products were BlackICE Desktop (a host-IPS for end-user systems) BlackICE Guard (an in-line network IPS) and BlackICE Sentry (a passive, IDS solution). NetworkICE was purchased in 2000 by Internet Security Systems (ISS). The BlackICE engine is still used in most ISS products, including the Proventia line of products.
Intrusion prevention systems may also serve secondarily at the host level to deny potentially malicious activity. There are advantages and disadvantages to host-based IPS compared with network-based IPS. In many cases, the technologies are thought to be complementary.
An Intrusion Prevention system must also be a very good Intrusion Detection system to enable a low rate of false positives. Some IPS systems can also prevent yet to be discovered attacks, such as those caused by a Buffer overflow.
Comparison to Intrusion detection systems (IDS)
IPS have many advantages over their legacy counterparts, intrusion detection systems (IDS). One advantage is they are designed to sit inline with traffic flows and prevent attacks in real-time. In addition, most IPS solutions have the ability to look at (decode) layer 7 protcols like HTTP, FTP, and SMTP which provides greater awareness. When deploying NIPS however, consideration should be given to whether the network segment is encrypted or not as many products are unable to support inspection of such traffic.
Types
Personal
See host based.
Host based
A host is a computer with a specific IP address. Intrusion-prevension systems (IPS) can be host or network based.
A host based IPS is one where the intrusion-prevention application is resident on that specific IP address (For example, this could be your PC system.)
A network based IPS is one where the IPS application/hardware and any actions taken to prevent an intrusion on a specific network host(s)is done from a host with another IP address on the network (This could be on a front-end firewall appliance.)
Network
Network intrusion prevention systems (NIPS) are purpose built hardware/software platforms that are designed to analyze, detect and report on security related events. NIPS are designed to inspect traffic and based on their configuration or security policy, they can drop malicious traffic.
Content based
Content based IPS (CBIPS) inspect the content of network packets for unique sequences, called signatures, to detect and hopefully prevent known types of attack such as worm infections and hacks.
Rate based
Rate based IPS (RBIPS) are primarily intended to prevent denial of service and Distributed Denial of Service attacks. They work by monitoring and learning normal network behaviors. Through real-time traffic monitoring and comparison with stored statistics, RBIPS can identify abnormal rates for certain types of traffic e.g. TCP, UDP or ARP packets, connections per second, packets per connection, packets to specific ports etc. Attacks are detected when thresholds are exceeded. The thresholds are dynamically adjusted based on time of day, day of the week etc., drawing on stored traffic statistics.
Unusual but legitimate network traffic patterns may create false alarms. The system's effectiveness is related to the granularity of the RBIPS rulebase and the quality of the stored statistics.
Once an attack is detected, various prevention techniques may be used such as rate-limiting specific attack-related traffic types, source or connection tracking, and source-address, port or protocol filtering (black-listing) or validation (white-listing).
Host based vs. network
- HIPS can handle all types of encrypted networks and can analyze all code.
- NIPS doesn't take processor and memory on the client/end-point/host.
- NIPS is a single point of failure; both good and bad. Easy administration, easy failure...