"asterisk" keeps calling our extensions, dead air on answer

Our PBX has been calling our extensions with the Caller-ID as asterisk. When we answer the call, it is just dead air.

When these calls happen, the phone on the extension just reads “asterisk”, without a number.

I’ve check our CDRs and trunks, and I don’t see any evidence of this happening from an outside source. Only in CDRs do we see a “s” as the origination…

Any ideas??