A wave of spam emails carrying malicious attachments infected with Cerber ransomware has hit corporate users of Microsoft's Office 365 service.
The attack began on June 22, shortly before 7:00 a.m. UTC when crooks used a new trick to let Cerber-infected spam bypass Microsoft's security defenses.
Cloud security platform, Avanan, says it took Microsoft about five hours to detect and begin blocking the malicious attachments.
However, by then, it was too late, says Avanan, as 57 percent of all businesses using Office 365 had received at least one copy of the ransomware in their inboxes.
There's nothing special about this version of Cerber , and this appears to be yet another case of scammers successfully bypassing Microsoft's spam filters. A similar incident occurred on June 1, when scammers bypassed Outlook and Hotmail spam filters and flooded users with spam for hours.
Cerber is one of the leading ransomware families today. According to data released by Fortinet at the end of May, Cerber ranks third in terms of infection detection behind the infamous CryptoWall and Locky.
If you need something to understand Cerber infections, then you should remember that this is a ransomware family that uses the OS text-to-speech feature to read the ransom note to users. Below is a screenshot of the malicious document that was downloaded in this recent campaign targeting corporate Microsoft Office 365 users.
