alert dns $HOME_NET any -> any any (msg:"ET MALWARE Linux/B1txor20 Backdoor Connectivity Check"; content:"|01|"; offset:2; depth:1; content:"|00 01 00 00 00 00 00|"; distance:1; within:7; content:"|06 67 6f 6f 67 6c 65 03 63 6f 6d 00 00 00 00 01|"; distance:1; within:16; endswith; fast_pattern; reference:url,blog.netlab.360.com/b1txor20-use-of-dns-tunneling_en/; classtype:trojan-activity; sid:2035526; rev:2; metadata:affected_product Linux, attack_target Client_Endpoint, created_at 2022_03_18, deployment Perimeter, deployment Internal, malware_family B1txor20, performance_impact Low, confidence High, signature_severity Major, updated_at 2022_03_18;)