alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE W32/Citadel.Arx Variant CnC Beacon 1"; flow:established,to_server; http.uri; content:"/rssfeed.php?a="; fast_pattern; pcre:"/^[^&]+?&\d+$/R"; http.header_names; to_lowercase; content:!"|0d 0a|referer|0d 0a|"; reference:url,botnetlegalnotice.com/citadel/files/Patel_Decl_Ex20.pdf; reference:url,www.fireeye.com/blog/technical/cyber-exploits/2013/11/the-dual-use-exploit-cve-2013-3906-used-in-both-targeted-attacks-and-crimeware-campaigns.html; classtype:command-and-control; sid:2017690; rev:4; metadata:attack_target Client_Endpoint, created_at 2013_11_07, deployment Perimeter, signature_severity Major, tag c2, updated_at 2024_04_20, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)