alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE r0 CnC Check"; flow:established,to_server; urilen:6; http.method; content:"GET"; http.uri; content:"/check"; fast_pattern; http.request_header; header_lowercase; content:"expect|3a 20|100-continue"; startswith; http.user_agent; content:"Mozilla/5.0 (Windows NT 6.3|3b 20|rv|3a|36.0) Gecko/20100101 Firefox/36.0"; http.header_names; to_lowercase; content:!"|0d 0a|referer|0d 0a|"; reference:url,blog.cari.net/carisirt-defaulting-on-passwords-part-1-r0_bot/; classtype:command-and-control; sid:2022105; rev:6; metadata:created_at 2015_11_17, signature_severity Major, updated_at 2024_04_28;)