BEC Campaigns Target Financial Execs via Office 365

A wave of ongoing business email compromise (BEC) campaigns has been targeting Office 365 accounts of business executives since March 2020. The attackers, dubbed Water Nue, have targeted execs at more than 1,000 companies, most recently those in senior roles in the US and Canada.

The primary targets are financial executives, who they spear-phish with the goal of stealing credentials to conduct further fraud. Their phishing emails redirect victims to fake Office 365 login pages. With stolen credentials, attackers send emails to the executives' subordinates containing invoices with altered banking info so they can try to steal funds via transfer requests.

Trend Micro researchers first noticed the campaign because of a large group of email domains used in these phishing attempts. They say Water Nue is interesting for a few reasons: While the group is successful in targeting high-level employees, its technical capabilities are limited. The attackers use basic phishing tools — no backdoors or Trojans — and rely on public cloud services.

The use of cloud services enabled attackers to obfuscate operations by hosting infrastructure in the services themselves, making it more difficult for forensics teams to spot their activity, the researchers report. This technique has become increasingly common among cybercriminals.

These techniques are not new, but they are effective: At the time Trend Micro shared its blog post on Aug. 6, Water Nue's attack attempts had collected more than 800 credentials from executives.

BEC attacks are a constant and expensive problem for organizations, which lost an estimated $1.77 billion to the threat in 2019, the FBI reported earlier this year. And they're growing more common: A report in late 2019 found a 269% spike in BEC attacks from the previous quarter.

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