VRT Advisories
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VRT Rules 2006-01-25
Sourcefire VRT Update
Date: 2006-01-25
Synopsis:
The Sourcefire VRT has been investigating the Black/Nyxem worm and its variants that are known to affect hosts using the Microsoft Windows operating system.
Details:
The VRT has done extensive analysis of the worm. The VRT has posted detailed pcaps from our lab here. You can also read a VRT engineer's candid review here.
The VRT has posted detailed pcaps of this worm from our lab. Users can download and view these pcaps here.
Initial reports from other sources make the following assertions about the worm behavior:
- Spreads mostly by email, and relies on people actually clicking on an attachment to infect themselves.
- Attempts to spread by SMB shares C$ and ADMIN$
- Hits a counter page that reports number of infected hosts. http://webstats.web.rcn.net/cgi-bin/Count.cgi?df=765247
- Attempts to check connectivity by hitting microsoft.com
From the initial binary analysis the VRT agrees with 1, 2, and 3. The worm is currently running in the lab to confirm all of these behaviors, and to confirm that the current rules in the VRT rule set will detect infected hosts.
The web stats counter for this worm is showing a large number of infections, however the accuracy of this counter can not be relied on since the counter does not verify the authenticity of the request. The VRT has not encountered any instances of infection whatsoever.
Infected hosts only make one request to the counter page, so our current opinion is that the best detection method for finding infected hosts is looking for attempts to spread via SMB shares, as it looks like it generates a large number of requests on this protocol.
In order to determine if an infection is in progress on a network, check Snort logs for the following SID's (these SID's detect attempts to connect to C$ and ADMIN$).
2177 NETBIOS SMB startup folder unicode access
2466 NETBIOS SMB-DS IPC$ unicode share access
2470 NETBIOS SMB C$ unicode share access
2472 NETBIOS SMB-DS C$ unicode share access
2473 NETBIOS SMB ADMIN$ unicode share access
2475 NETBIOS SMB-DS ADMIN$ unicode share access
1042 WEB-IIS view source via translate header
1149 WEB-CGI count.cgi access
1917 SCAN UPnP service discover attempt
466 ICMP L3retriever Ping
538 NETBIOS SMB IPC$ unicode share access
Additionally, the IP address for webstats.web.rcn.net has not changed in days so an alternate detection method may be to try the following rule to find hosts as they get infected.
alert tcp $HOME_NET any -> 207.172.16.155 80 (msg:"COMMUNITY VIRUS Possible BlackWorm or Nymex infected host"; uricontent:"/cgi-bin/Count.cgi?df=765247"; sid:100000226; rev:1;)
It should be noted however, that subsequent variants of the worm may display different behavior and this rule could be subject to generating false negative events.
This rule is in the latest Community rule pack and is identified as sid 100000197. If this rule proves correct in the lab and can be improved upon, the VRT will update the VRT Certified Ruleset accordingly.
Additional References:
Symantec
http://www.sarc.com/avcenter/venc/data/w32.blackmal.e@mm.html
McAfee
http://vil.nai.com/vil/content/v_138027.htm
F-Secure
http://www.f-secure.fi/v-descs/nyxem_e.shtml
CA
http://www3.ca.com/securityadvisor/virusinfo/virus.aspx?id=50198
About the VRT:
The Sourcefire VRT is a group of leading edge intrusion detection and prevention experts working to proactively discover, assess and respond to the latest trends in hacking activity, intrusion attempts and vulnerabilities. This team is also supported by the vast resources of the open source Snort community, making it the largest group dedicated to advances in network security industry.
Posted by on Jan 25, 2006
VRT Rules 2006-01-05
Sourcefire VRT Update
Date: 2006-01-05
Synopsis:
The Sourcefire Vulnerability Research Team (VRT) has improved detection for the new Sober worm variant.
Details:
The Sober worm is a mass mailer normally spread via email. A variant of this worm displays more infection indicators that can be detected easily using rules.
Rules to detect machines infected with this variant of the sober worm are included in this update and are identified as sids 5320 and 5324.
Additionally, Sourcefire RNA customers can utilize the capabilities of their RNA applicance to detect infections.
Rule Pack Summary:
For a complete list of new and modified rules, click here.
Warning:
Sourcefire VRT rule packs often utilize enhancements made to Snort. Operators should upgrade to the latest revision or patch level for Snort to ensure these enhancements are available before using these rules.
About the VRT:
The Sourcefire VRT is a group of leading edge intrusion detection and prevention experts working to proactively discover, assess and respond to the latest trends in hacking activity, intrusion attempts and vulnerabilities. This team is also supported by the vast resources of the open source Snort community, making it the largest group dedicated to advances in network security industry.
Posted by on Jan 05, 2006
VRT Rules 2005-12-30
Sourcefire VRT Update
Date: 2005-12-30
Synopsis:
The Sourcefire Vulnerability Research Team (VRT) has learned of multiple vulnerabilities affecting hosts using the Microsoft operating system. The VRT has also learned of a new Sober worm variant that displays uniquely detectable infection characteristics.
Details:
The Microsoft Windows graphics rendering engine does not correctly parse windows metafile (wmf) format files. As a result, viewing a corrupted file may present an attacker with the opportunity to execute code of their choosing.
The Sourcefire VRT has confirmed that a rule identified as sid 2436, released on May 21, 2004, will generate events when an attempt is made to exploit this vulnerability. Also, rules to detect attacks targeting this vulnerability are included in this update and are identified as sids 5318 and 5319.
Note: Due to the possibility of a high false positive rate, sid 5318 is not enabled by default.
WARNING: To reduce the possibility of evasion, http_inspect needs to be configured with "flow_depth 0" so that it can inspect all the traffic from HTTP server responses. Setting flow_depth 0 will cause performance problems in some situations.
The Sober worm is a mass mailer normally spread via email. A variant of this worm displays more infection indicators that can be detected easily using rules.
Rules to detect machines infected with this variant of the sober worm are included in this update and are identified as sids 5321 through 5323.
Rule Pack Summary:
For a complete list of new and modified rules, click here.
Warning:
Sourcefire VRT rule packs often utilize enhancements made to Snort. Operators should upgrade to the latest revision or patch level for Snort to ensure these enhancements are available before using these rules.
About the VRT:
The Sourcefire VRT is a group of leading edge intrusion detection and prevention experts working to proactively discover, assess and respond to the latest trends in hacking activity, intrusion attempts and vulnerabilities. This team is also supported by the vast resources of the open source Snort community, making it the largest group dedicated to advances in network security industry.
Posted by on Dec 30, 2005
VRT Rules 2005-12-14
Sourcefire VRT Update
Date: 2005-12-14
Synopsis:
The Sourcefire Vulnerability Research Team (VRT) has learned of multiple vulnerabilities affecting hosts using the Microsoft operating system.
Details:
Microsoft Security Bulletin MS05-054 A vulnerability exists in the way that Internet Explorer handles COM objects that should not be used by Internet Explorer. When Internet Explorer tries to use these COM objects as ActiveX controls, an attacker may be presented with the opportunity to execute code of their choosing on the target system.
Rules to detect attacks targeting this vulnerability are included in this update and are identified as sids 4890 through 4915.
A vulnerability exists in the way Internet Explorer handles the window() function supplied to the javascript "onload" handler as a parameter. The conditions for exploitation occur when a page is opened in the browser that uses <body onload=window();>
The Sourcefire VRT has confirmed that a rule identified as sid 4647, released on November 9, 2005, will generate events when an attempt is made to exploit this vulnerability.
Rule Pack Summary:
For a complete list of new and modified rules, click here.
Warning:
Sourcefire VRT rule packs often utilize enhancements made to Snort. Operators should upgrade to the latest revision or patch level for Snort to ensure these enhancements are available before using these rules.
About the VRT:
The Sourcefire VRT is a group of leading edge intrusion detection and prevention experts working to proactively discover, assess and respond to the latest trends in hacking activity, intrusion attempts and vulnerabilities. This team is also supported by the vast resources of the open source Snort community, making it the largest group dedicated to advances in network security industry.
Posted by on Dec 14, 2005
VRT Rules 2005-12-08
Sourcefire VRT Certified Rules Update
Date: 2005-12-08
Synopsis:
The Sourcefire Vulnerability Research Team (VRT) has learned of a vulnerability in the Symantec AntiVirus Web Interface. In addition, the Sourcefire VRT has made numerous rule reference additions to existing rules in order to provide users more context for generated events.
Details:
A buffer overflow vulnerability exists in the Symantec AntiVirus Scan Engine Web Service Administrative Interface. The vulnerability exists because user supplied data is not properly checked before processing.
A rule to detect attacks targeting this vulnerability is included in this update and is identified as sid 4681.
The Sourcefire Vulnerability Research Team (VRT) has made numerous rule reference additions to existing rules and has added a number of new rules to provide coverage for additional attack vectors for existing vulnerabilities.
Rule Pack Summary:
For a complete list of new and modified rules, click here.
Warning:
Sourcefire VRT rule packs often utilize enhancements made to Snort. Operators should upgrade to the latest revision or patch level for Snort to ensure these enhancements are available before using these rules.
About the VRT:
The Sourcefire VRT is a group of leading edge intrusion detection and prevention experts working to proactively discover, assess and respond to the latest trends in hacking activity, intrusion attempts and vulnerabilities. This team is also supported by the vast resources of the open source Snort community, making it the largest group dedicated to advances in network security industry.
Posted by on Dec 08, 2005
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