Nigel, Removed isc.incidents.org reference since it is no longer active.Rule:--Sid:1889--Summary:This event is generated when a web server infected by the slapper worm attempts to send traffic via a communication channel. --Impact:Remote access and potentially denial of service.  A slapper worm infection indicates a successful compromise of the host.  A communication channel established between infected hosts can be used as a vehicle for a distributed denial of service attack of a target host or network.--Detailed Information:The Apache/mod_ssl worm, also known as slapper, exploits a vulnerability associated with certain versions of OpenSSL.  Once a host has been infected by the worm, the worm then attempts to establish a communication channel using UDP port 2002 (both source and destination) to the infecting host.  This communication channel is used to create a network for infected hosts to communicate with each other to identify other infected hosts and to deliver attack instructions for other sites.--Affected Systems:Linux hosts running Apache with mod_ssl using SSLv2-enabled OpenSSL 0.9.6d or earlier on Intel x86 architectures.--Attack Scenarios:The communication channel created by the slapper worm allows infected hosts to receive direction from other infected hosts.  This can be used, for instance, to coordinate a DDoS attack.--Ease of Attack:Simple.  Exploit code exists. --False Positives:None Known.--False Negatives:It has been observed that the port number for the communication channel may vary.  Ports 1978 and 4156 have also been seen.--Corrective Action:Apply the appropriate patch or upgrade to the most current version of OpenSSL.--Contributors:Original rule writer unknown.Sourcefire Research TeamJudy Novak <judy.novak@sourcefire.com>--Additional References:CERThttp://www.cert.org/advisories/CA-2002-27.html--