alert tcp $EXTERNAL_NET 1024:5000 -> $HOME_NET 1024:65535 (msg:"ET INFO SOCKSv4 HTTP Proxy Inbound Request (Windows Source)"; dsize:9<>18; flow:established,to_server; content:"|04 01 00 50|"; depth:4; threshold:type both, track by_src, count 1, seconds 900; reference:url,handlers.sans.org/wsalusky/rants/; reference:url,en.wikipedia.org/wiki/SOCKS; reference:url,ss5.sourceforge.net/socks4.protocol.txt; reference:url,ss5.sourceforge.net/socks4A.protocol.txt; reference:url,www.ietf.org/rfc/rfc1928.txt; reference:url,www.ietf.org/rfc/rfc1929.txt; reference:url,www.ietf.org/rfc/rfc1961.txt; reference:url,www.ietf.org/rfc/rfc3089.txt; classtype:protocol-command-decode; sid:2003262; rev:6; metadata:created_at 2010_07_30, confidence High, signature_severity Informational, updated_at 2019_07_26;)