Microsoft has quietly seized control of several domains that were used in COVID-19-themed attacks against its customers over the past several months.
The US District Court for the Eastern District of Virginia had earlier granted the company permission to seize the domains after Microsoft had filed a civil complaint about the attacks causing it "irreparable and ongoing harm."
Tom Burt, Microsoft corporate vice president, customer security and trust, today likened the attacks to a form of business email compromise that targeted customers in 62 countries.
The attacks first began in December 2019 and involved phishing emails designed to look like they originated from the recipient's employer or other trusted source. Many of the emails were directed at business leaders in a variety of industries and — initially, at least — contained messages pertaining to common business activities. When a recipient clicked the embedded link in these emails, it led to a sequence of events that ended with the user being prompted to grant access privileges to a malicious web app.
The fraudulently obtained privileges gave the attackers full access to the victim's Office 365 account, including email, contact lists, and data stored in OneDrive for Business and in corporate SharePoint document management and storage systems. Unlike typical phishing scams, the attackers in this case were able to gain full, unauthorized access to Office 365 accounts without requiring victims to share their usernames or passwords via fake websites and other interfaces, Burt said in a blog post.
"After clicking through the consent prompt for the malicious web app, the victim unwittingly granted criminals permission to access and control the victims' Office 365 account contents," he noted.
Microsoft was able to stop the original wave of attacks using "technical means" to block the criminals and disable the malicious web applications, Burt said, without elaborating on what those measures were.
However, Microsoft recently observed renewed attempts by the same attackers to gain access to Office 365 accounts, this time using COVID-19-themed lures. The new attacks involved millions of phishing emails being sent to Microsoft business users in more than five dozen countries, prompting the company to seek legal action. In its complaint, Microsoft described the scale of the attacks as "immense" and said the criminals posed an ongoing risk because of their ability to create and deploy new malicious web apps using their existing infrastructure.
Unique Civil Case
"This unique civil case against COVID-19-themed BEC attacks has allowed us to proactively disable key domains that are part of the criminals' malicious infrastructure, which is a critical step in protecting our customers," Burt said.
It's unclear when exactly Microsoft seized control of the allegedly malicious domains or even how many of them it has seized so far. The company's complaint lists six dot-com domains that it said were being used as infrastructure for carrying out the attacks. Each of the domains had names that suggest a connection to Microsoft Office products. Domain registration service Namecheap was listed as the registrar for five of the domains identified in Microsoft's complaint and GoDaddy LLC for the sixth.
COVID-19-themed attacks, such as those targeting Microsoft Office 365 accounts, have become very common over the past several months. Threat actors have been attempting to take advantage of the global concern around the pandemic with email and social engineering lures pertaining to COVID-19-related topics, such as purported cures for the vaccine or some new development related to the virus. Often the lures have led unsuspecting users to malware-laden websites or to fake web pages designed to steal their credentials. Attackers have registered thousands of coronavirus-themed domains in the past several months to scam unsuspecting Internet users in a variety of ways.
The trend has forced organizations to look more closely at new measures and approaches — such as zero trust — for protecting their networks and data against infected systems belonging to employees working from home.