This may or may not already have been posted: Transmission (BT app) urgent security update. Possibly infected with KeyRanger (Cryptolocker-style malware [9to5mac.com]
Symptoms:
- "kernel_service" process running
- Existence of "/Applications/Transmission.app/Contents/Resources/General.rtf" or /Applications/Transmission.app/Contents/Resources/ General.rtf"
- Existence of ".kernel_pid", ".kerneltime", ".kernelcomplete", or "kernel_service" files in ~/Library (note the hidden files)