alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"ET WEB_SERVER base64_decode in UA"; flow:established,to_server; http.user_agent; content:"base64_decode("; nocase; fast_pattern; reference:url,blog.spiderlabs.com/2013/02/honeypot-alert-user-agent-field-php-injection-attacks.html; classtype:bad-unknown; sid:2016416; rev:5; metadata:created_at 2013_02_16, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_18;)