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Over 600 Microsoft Subdomains Can Be Hijacked: Researchers

There are more than 600 legitimate Microsoft subdomains that can be hijacked and abused for phishing, malware delivery and scams, researchers warned this week.

There are more than 600 legitimate Microsoft subdomains that can be hijacked and abused for phishing, malware delivery and scams, researchers warned this week.

The problem affects many big companies and it has been known for years. The DNS records for a subdomain point to a domain that no longer exists. Anyone who creates the non-existent domain can basically hijack the subdomain that has the misconfigured DNS records.

An attacker can direct the visitors of the hijacked subdomain to a phishing website and capture their authentication credentials or other sensitive information, trick them into installing malware, trick them into uploading sensitive files, or scam them.

Researchers at Vullnerability, a company that specializes in exploit and vulnerability alerting services, have created an automated system that scanned all the subdomains of some important Microsoft domains. The scan revealed the existence of over 670 subdomains that could be hijacked using this technique.

The researchers reported a dozen of the impacted subdomains to Microsoft and the tech giant has taken steps to prevent them from being hijacked. These subdomains included,,, and

However, they will not provide the entire list of affected subdomains to Microsoft unless the company starts rewarding these types of security issues through its bug bounty programs. The experts have published a blog post describing their findings and a video showing how the attack works.

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“We are aware of such reports and are taking appropriate action as needed to help protect Microsoft services and customers,” a Microsoft spokesperson told SecurityWeek.

The company also noted that this is a common attack method that involves getting the targeted user to click on a specially crafted link delivered via email or a chat service. The threat can be mitigated by following best practices and exercising caution when opening links or files from untrusted sources.

Experts have been warning about the risks posed by subdomain hijacking for years and ZDNet reported last month that spammers had already started hijacking Microsoft subdomains. Microsoft took steps to address the issue, but as the Vullnerability research shows there are still hundreds of domains that could be abused.

“This vulnerability is potentially widespread and insidious,” Kevin O’Brien, co-founder and CEO of cloud email security firm GreatHorn, told SecurityWeek. “By hijacking Microsoft subdomains, which are often whitelisted, phishing attempts can bypass even the most elite anti-spam and email security tools, most of which conduct checks at the domain level rather than the subdomain level. And although the security industry has long attributed breaches and successful phishing attacks to poorly educated or careless users, this technique reinforces that criminals can—with relatively little effort—create highly sophisticated and believable phishing campaigns that can fool even the savviest of users.”

A report published last month by cybersecurity firm Webroot showed that nearly a quarter of malicious URLs spotted last year were hosted on non-malicious domains.

Related: DHS Warns Federal Agencies of DNS Hijacking Attacks

Related: Ongoing DNS Hijacking Campaign Targets Gmail, PayPal, Netflix Users

Related: Iran-Linked DNS Hijacking Attacks Target Organizations Worldwide

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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