Unknown user deleting files from different IPs

Hello,

Recently a number of entries were made in the Audit Log with the following pattern:

Description

deleted WPHB Minify Group “34970c23330f783c770f6daea8099319-scripts”

Context Type IP address User Date / Time

WPHB Minify Group Content 78.46.79.137 Guest December 9, 2017 3:24 am

There are a lot of entries like this and there is no user associated with the entry. Many of the entries have different user IP but there are some clusters.

Thanks kindly,