[It's undocumented, but after I wrote this I discovered the Antivirus 9 install puts an app called 'Remove Sophos Anti-Virus' in the Applications folder.]
In a moment of madness, I installed Sophos Antivirus.
Forgive me, I have sinned. It's a mess.
Unfortunately, the online documentation for version 9 removal is incorrect: Using the Terminal to install or remove Sophos Anti-Virus for Mac OS X. 'Remove Sophos Anti-Virus.pkg' no longer exists and there's no longer a GUI uninstaller.
Instead you have to run remove_v9.sh. I tried to do that from my Admin account -- but that failed. You have to run it from the account it was installed from, even though this app is a root install and the original user account might not be an admin account. This worked from my non-admin account in OS X Mountain Lion where Admin is my Administrator account:
jfaughnan$ su Admin Password: bash-3.2$ cd /Library/Sophos\ Anti-Virus bash-3.2$ sudo /Library/Sophos\ Anti-Virus/remove_v9.sh Password:
I got this ...
WARNING: this script permenantly removes Sophos Anti-Virus for Mac version 9 it should NOT be used on a version 8 installation
if there are errors reported by this script, run it again (it fixes itself)
press control-C now to abort (automatically continues in 5 seconds) run with -f (next time) to skip the 5 second delay ..... removing launchagent com.sophos.uiserver for user 502 removing /Library/LaunchAgents/com.sophos.uiserver.plist stopping Sophos Anti-Virus.app removing /Applications/Sophos Anti-Virus.app removing /Library/Sophos Anti-Virus removing /Library/Frameworks/SAVI.framework removing /Library/Frameworks/SUMScanKit.framework removing /Library/Application Support/Sophos removing /Library/Caches/com.sophos.sav removing /Library/Caches/com.sophos.sau removing /Library/Preferences/com.sophos.sau.plist removing /usr/bin/SophosUpdate removing /usr/bin/sweep done error: leftover path /Library/Caches/com.sophos.installer/ needs to be removed error: leftover path /Library/Caches/com.sophos.sxld/ needs to be removed bash-3.2$
error: leftover path /Applications/Sophos Anti-Virus.app/ needs to be removed error: leftover path /Library/Frameworks/SAVI.framework/ needs to be removed error: leftover path /Library/Frameworks/SUMScanKit.framework/ needs to be removed error: leftover path /Library/Sophos Anti-Virus/ needs to be removed error: leftover path /Library/Caches/com.sophos.installer/ needs to be removed error: leftover path /Library/Caches/com.sophos.sau/ needs to be removed error: leftover path /Library/Caches/com.sophos.sav/ needs to be removed error: leftover path /Library/Caches/com.sophos.sxld/ needs to be removed error: leftover path /Library/LaunchAgents/com.sophos.uiserver.plist needs to be removed
What a mess.