Never mind, it does appear to have a code signature by Performiks OOO. I use Little Snitch alongside AdGuard, so this is the information it provided me on AdGuard trying to connect via adguard-tcpkill.@xx_
Adguard-tcpkill is closing needed browser connections to filter it all.
codesign --verbose -v adguard-tcpkill
adguard-tcpkill: valid on disk
adguard-tcpkill: satisfies its Designated Requirement
What actually did you use to check in signed status?