Developed by Robert “RSnake” Hansen, Slowloris is DDoS attack software that permits one computer to require down an internet server. Due the straightforward yet elegant nature of this attack, it requires minimal bandwidth to implement and affects the target server’s web server only, with almost no side effects on other services and ports.
Slowloris has proven highly-effective against many popular sorts of web server software, including Apache 1.x and 2.x.
Over the years, Slowloris has been credited with variety of high-profile server takedowns. Notably, it had been used extensively by Iranian ‘hackivists’ following the 2009 Iranian presidential election to attack Iranian government internet sites .
Slowloris works by opening multiple connections to the targeted web server and keeping them open as long as possible. It does this by continuously sending partial HTTP requests, none of which are ever completed. The attacked servers open more and connections open, expecting each of the attack requests to be completed.
Periodically, the Slowloris sends subsequent HTTP headers for every request, but never actually completes the request. Ultimately, the targeted server’s maximum concurrent connection pool is filled, and extra (legitimate) connection attempts are denied.
By sending partial, as against malformed, packets, Slowloris can easily elapse traditional Intrusion Detection systems.
Named after a kind of slow-moving Asian primate, Slowloris really does win the race by moving slowly and steadily. A Slowloris attack must await sockets to be released by legitimate requests before consuming them one by one.
For a high-volume internet site , this will take a while . the method are often further slowed if legitimate sessions are reinitiated. But within the end, if the attack is unmitigated, Slowloris—like the tortoise—wins the race.
If undetected or unmitigated, Slowloris attacks also can last for long periods of your time . When attacked sockets outing , Slowloris simply reinitiates the connections, continuing to reach the online server until mitigated.
Designed for stealth also as efficacy, Slowloris are often modified to send different host headers within the event that a virtual host is targeted, and logs are stored separately for every virtual host.
More importantly, within the course of an attack, Slowloris are often set to suppress log file creation. this suggests the attack can catch unmonitored servers off-guard, with none red flags appearing in log file entries.
Methods of mitigation
Imperva’s security services are enabled by reverse proxy technology, used for inspection of all incoming requests on their thanks to the clients’ servers.
Imperva’s secured proxy won’t forward any partial connection requests—rendering all Slowloris DDoS attack attempts completely and utterly useless.
