Researchers at VIPRE Security observed a 276% increase in malware delivered by phishing between Q1 and Q4 of 2023.
“Last year, our YARA rules caught between one and two million generic malware instances each quarter, with a nearly 20% jump in Q4,” VIPRE’s report says. “The numbers were significantly less for specific instances, ranging from 70,000 – 400,000, but the Q4 jump exceeded 200%.”
VIPRE also observed a notable increase in the use of .eml files to smuggle malicious content past email security filters.
“[EML] is the format an email takes when you send or save it in a plain text version, like when you want to forward a batch of old emails to a new address,” the researchers write. “Cybercriminals will place the malicious content inside the .eml file, which gets attached to the actual phishing email and subsequently overlooked by many email security solutions. The fact that this type of file extension is seen so rarely in the business world (but does still happen) increases user curiosity and therefore, chances of opening the .eml file and following its direction, whether it be clicking on a link, opening a web page, or providing credentials.”
Additionally, the researchers warn that HTML files accounted for more than half of malicious attachments in 2023.
“This is the first year .eml attachments have made the list in any significant way. Companies would be wise to spot the trend and prepare their users now,” the report says. “Last year, we flagged a growing uptick in HTML usage, and this year it was our primary contender. Significantly, HTML attachments declined by 27% by year’s end, but PDFs rose by over 100% and EMLs by a drastic 4600%.”
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