PING VIRUS???

[HurricaneIndy]

Lately my network has been swamped!! Cut off our internet connection. Then
after probing our network it turns out some computers had TONS of CMD.exe and
PING.exe running!!! These boxes were PINGing like crazy killing the network.

Has anyone encountered this or can point me to how we got it and how to
rectify it?
Thanks...

Indy