February 23, 2024

New BEC cyberattacks use phishing with a legit Dropbox hyperlink as a lure for malware and credentials theft.

This illustration shows a lock, unlocked over a person at a keyboard.
Picture: Adobe Inventory.

Risk actors have added a brand new wrinkle to conventional enterprise e-mail compromise cyberattacks. Name it BEC 3.0 — phishing assaults that bury the hook in legit net providers like Dropbox.

Avanan, a unit of Test Level Software program, has tracked a current instance of this assault household, during which hackers created free Dropbox accounts to seize credentials or conceal malware in legitimate-looking, contextually related paperwork equivalent to potential staff’ resumes.

The assault, the safety agency found, began with the actors sharing a PDF of somebody’s resume through Dropbox. The goal can’t view the doc except they Add To Dropbox. The hyperlink from Dropbox regarded legit, making the exploit harder to identify.

The phishing exploit entails these steps:

  • First, a person clicks the hyperlink in a legit notification from Dropbox to a resume and accesses a web page hosted on the file-sharing service.
  • The person should then enter their e-mail account and password to view the doc. Because of this the risk actors have entry to e-mail addresses and passwords.

On this web page hosted on Dropbox, customers are requested to enter their e-mail account and password to view the doc, giving risk actors person credentials.

As soon as a person enters their credentials, they’re directed to a pretend Microsoft OneDrive hyperlink. By clicking on the hyperlink, customers are given a malicious obtain.

“We’ve seen hackers do a whole lot of BEC assaults,” Jeremy Fuchs, a cybersecurity researcher/analyst at Avanan, stated in a report on the assault. “These assaults have a number of variations, however usually they attempt to spoof an govt or associate to get an finish person to do one thing they don’t wish to do (like pay an bill to the fallacious place),” he stated.

SEE: One other hide-the-malware assault focuses on DNS (TechRepublic)

“Leveraging legit web sites to host malicious content material is a surefire technique to get into the inbox,” he stated. “Most safety providers will take a look at the sender — on this case, Dropbox — and see that it’s legit and settle for the message. That’s as a result of it’s legit,” he added.

Avanan stated stopping these stealth assaults requires quite a few defensive steps, together with scanning for malicious information in Dropbox and hyperlinks in paperwork, in addition to changing hyperlinks within the e-mail physique and inside attachments. The important thing to training towards these social engineering assaults is context, in accordance with Fuchs: “Are resumes sometimes despatched through Dropbox? If not, it could be a cause to contact the unique sender and double-check. If they’re, take it one step additional. Whenever you log into Dropbox, do I’ve to log in once more with my e-mail?”

Avanan stated the researchers reached out to Dropbox on Could 15 to tell them of this assault and analysis.

Linktree additionally used to seize credentials

Earlier this month, Avanan found the same hack utilizing the social media reference touchdown web page Linktree, which is hosted on websites like Instagram and TikTok. Much like the Dropbox assaults, hackers created legit Linktree pages to host malicious URLs to reap credentials.

The attackers despatched targets spoofed Microsoft OneDrive or SharePoint notifications {that a} file has been shared with them, instructing them to open the file, in accordance with Avanan. In the end, the person is redirected to a pretend Workplace 365 login web page, the place they’re requested to enter their credentials, the place their credentials are stolen.

“[Users] ought to suppose: Why would this particular person ship me a doc through Linktree? Most definitely, that wouldn’t be the case. That’s all part of safety consciousness — understanding if an e-mail or course of appears logical,” stated Fuchs.

In these instances, the agency means that recipients:

  • All the time examine the sender’s handle earlier than replying to an e-mail.
  • Cease and suppose if the medium getting used to ship a file is typical.
  • When logging right into a web page, double-check the URL to see if it’s Microsoft or one other legit website.

BEC assaults utilizing legit websites could escalate this yr

Fuchs stated there aren’t any apparent visible cues to tip off assault recipients to BEC exploits. “Though if you happen to have been to signal into the Dropbox web page, you’d see that there’s a OneDrive emblem and hyperlink,” he stated. “Eagle-eyed customers ought to discover that discrepancy and suppose—why would there be two competing providers on one web page?,” he added.

He predicted that these assaults will escalate. “Any fashionable service that’s legit can probably be used as a car to ship this kind of malicious exercise. That’s why we count on it to take off within the close to future,” he stated, including that the exploit has been used tens of 1000’s of instances. “We consider this may actually take off in quantity within the second half of the yr,” he stated.