Phantom voicemail

hi all, new to the forum, and pretty much new to asterisk.
client having an issue with phantom voicemails arriving in one voicemail (the main secretary voicemail) overnight, at least once a week, all exactly the same time (31secs) after one another. sometimes, it can be around 10-15, sometimes 30-60 calls. is this an attack on a pbx?

cheers
inc

Sounds like it.

Look in the logs …

Ian