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Application Security

Microsoft Cracks Down on Malicious Homoglyph Domains

Microsoft on Monday announced that it secured a court order to take down numerous malicious homoglyph domains that a criminal group registered to impersonate legitimate sites of various businesses, predominantly located in North America.

Microsoft on Monday announced that it secured a court order to take down numerous malicious homoglyph domains that a criminal group registered to impersonate legitimate sites of various businesses, predominantly located in North America.

Leveraging similarities between alpha-numeric characters, cybercriminals register homoglyph domains that closely resemble those of legitimate businesses, but are instead under the control of the unauthorized parties.

The technique is often used in business email compromise (BEC) attacks, but is also employed by nation-state adversaries and in malware and ransomware distribution campaigns, for network compromise, combined with credential phishing and account compromise.

The crime group that Microsoft took action against registered close to 20 malicious homoglyph domains, mainly mimicking the legitimate sites of small businesses in North America, across multiple industries.

Microsoft believes that the financially motivated hackers might be part of an extensive network based out of West Africa.

The attackers leveraged the fraudulent domains and stolen credentials to unlawfully access and monitor accounts, gather intelligence, and impersonate Microsoft customers to trick victims into sending money to them.

[ Related: A Zero-Day Homograph Domain Name Attack ]

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“Once the criminals gained access to a network, they imitated customer employees and targeted their trusted networks, vendors, contractors and agents in an effort to deceive them into sending or approving fraudulent financial payments,” Microsoft said in a blog post.

In one instance, the attackers hijacked legitimate Office 365 e-mail communication to send an impersonation email from a homoglyph domain (that had a single letter changed) and convince the victim that the message came from a known trusted source. They then falsely claimed that the CFO put a hold on the account, asking for a payment to be made as soon as quickly.

To ensure that the attackers can’t continue their nefarious activity even if they move their infrastructure outside the Microsoft ecosystem, Redmond secured an order to ask third-party service providers to terminate the fraudulent domains.

“The action will further allow us to diminish the criminals’ capabilities and, more importantly, obtain additional evidence to undertake further disruptions inside and outside court,” Microsoft says, adding that the use of homoglyph domains is trending up among cybercriminals.

Related: A Zero-Day Homograph Domain Name Attack

Related: Internet Security Threats from a Multilingual Domain Name System

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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