The storm center handlers mailbox has received a growing number of email inquiries regarding root cause for Windows domain account lockouts which we most likely attribute to the infection base of Downadup/Conficker malware variants. Downadup/Conficker malware (actual naming is dependant upon your AV product) due to the integration of exploit code for the (MS08-067) RPC service vulnerability, if present on even a single host within any private network may quickly result in mass domain account lock outs where failed password attempt policies are in force.
FYI, Recent handler diaries related to Downadup/Conficker malware have been published by fellow handlers Lenny Zeltser: [http://isc.sans.org/diary.html?storyid=5653], and Patrick Nolan: [http://isc.sans.org/diary.html?storyid=5401].
On the note of proactive mitigations, F-Secure has published a blog today detailing a list of Downadup domains that have been determined will be leveraged *this week* by ongoing Downadup infections at: [http://www.f-secure.com/weblog/archives/00001578.html]. The F-Secure published host/domain blocklist is available directly via: [http://www.f-secure.com/weblog/archives/downadup_domain_blocklist_13_16.txt]. For additional technical background on Downadup malware, F-Secure malware detail is published at: [http://www.f-secure.com/v-descs/worm_w32_downadup_al.shtml].
The F-Secure published pre-emptive host block list was also referenced by [http://malwaredomains.com/?p=353]. This domain list makes an excellent candidate list for inclusion in blocklisting efforts by any organization who applies DNS based blocking/protective mechanisms in the attempt to prevent access to known malicious hosting/sites.
* The unique IP list (based on currently resolving hostnames from the F-Secure list) point to a mix of the following addresses and may change before this threat 'goes live'.
ASN | IP Address | AS Name
3561 | 18.104.22.168 | SAVVIS - Savvis
9120 | 22.214.171.124 | COHAESIONET Cohaesio A/S
10228 | 126.96.36.199 | YAHOO-CN Internet Content Provider
20860 | 188.8.131.52 | IOMART-AS Iomart Hosting Network Services
24940 | 184.108.40.206 | HETZNER-AS Hetzner Online AG RZ-Nuernberg
40142 | 220.127.116.11 | BGP1-AMP-TECHNOLOGY - Amp Technology, LLC
IP based blocking measures should be considered very carefully as blocking host IP targets may introduce collateral damage where access to legitimate sites can be blocked if mass virtual hosting services are leveraged as temporary pointers by the Downadup/Conficker host list. The Yahoo business hosting VIP above is a prime example of where collateral damage by IP based blocking would be encountered.
Handler on Duty - ;)