Possible agents:

- Detect if a user is connected from more than one different address.
- Detect if root is logged in remotely.
DONE (CheckInet, CheckInetPeriodic) - Detect multiple service requests to a single port from a single host.
PARTIALLY DONE (WeirdConn) - Detect port scans
DONE (FailedLogins) - Detect multiple invalid login attempts
DONE (DiskSpace, SpaceTmp) - Monitor disk for low free space.
DONE (CheckNFSserver) - Detect NFS server failures.
