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Security Activity Bulletin

Slowloris Multiple HTTP Server Denial of Service Attack Tool

 
Threat Type:IntelliShield: Applied Mitigation Bulletin
IntelliShield ID:18544
Version:1
First Published:2009 June 18 18:26 GMT
Last Published:2009 June 18 18:26 GMT
Port: 80
Urgency:Possible use
Credibility:Highly Credible
Severity:Mild Damage
 
Version Summary:

Slowloris, an attack tool that could allow an unauthenticated, remote attacker to exhaust available connections on targeted HTTP servers, has been publicly released.

 

Description
 

Slowloris, an attack tool that could allow an unauthenticated, remote attacker to exhaust available connections on targeted HTTP servers, has been publicly released.

The tool is designed to slowly send incomplete HTTP requests to an HTTP server.? The format of the request could cause the server to continue to wait for input on an established connection.? Sending the malicious HTTP requests requires little bandwidth on the behalf of the attacker, decreasing the network resources required for exploitation.? By using the tool, an attacker could?cause the targeted server to become unresponsive and unable to process further requests due to the exhaustion of allowed HTTP connections.

HTTP servers that are known to be affected include the Apache HTTP Server and the Squid HTTP Proxy.? Microsoft IIS Servers version 6.0 and 7.0 are reportedly unaffected by the tool.? Sites configured with load balancers may be at less?risk of isolated attack because a single attack host?could be unable to send enough requests to exhaust HTTP connections.? Network filtering, including the use of intrusion prevention service (IPS)?devices, may block malformed HTTP requests.

No attacks involving use of the tool have been publicly reported.? Administrators are advised to monitor critical systems for signs of exploitation.


Signatures
 
Cisco Intrusion Prevention System (IPS) 6.0
Signature IDSignature NameReleaseLatest Release Date
1034/0Slowloris ExploitS6672012 Sep 13 
 
Alert History
 

Initial Release



Product Sets
 
The security vulnerability applies to the following combinations of products.

Primary Products:
IntelliShieldSecurity Activity Bulletin Original Release Base

Associated Products:
N/A




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