Over the last three months there has been a major increase in the number of email-based attacks using malicious Windows Script File (WSF) attachments – particularly done by ransomware groups.
That’s according to Symantec who has worked to block a number of major campaigns involving the files.
WSF files are designed to allow a mix of scripting languages within a single file which Symantec explains are opened and run by the Windows Script Host (WSH).
According to Symantec, malicious WSF files have been used in a number of recent major spam campaigns spreading Locky.
For example, between October 3 and 4, Symantec blocked more than 1.3 million emails with the subject line "Travel Itinerary."
The emails claimed to come from a major airline and came with an attachment that consisted of a WSF file within a .zip archive.
If the WSF file was allowed to run, Locky was installed on the victim's computer.
Not long after, on October 5, the same attack group launched another massive malicious spam campaign with the subject line "complaint letter."
Symantec says it was able to block more than 918,000 of these emails and explains that the campaigns are part of a broader trend.
Over the past few months, the cyber security organisation has noticed a major increase in the overall numbers of emails being blocked containing malicious WSF attachments.
In June there were just over 22,000 with the figure shooting up to more than 2 million in July. September was a record month, with more than 2.2 million emails blocked.
For constant protection, Symantec advises to regularly back up any files, keep security software up to date and always delete any suspicious looking emails.