America's small businesses face the brunt of China's Exchange server hacks

Zack Whittaker
·5-min read

As the U.S. reportedly readies for retaliation against Russia for hacking into some of the government's most sensitive federal networks, the U.S. is facing another old adversary in cyberspace: China.

Microsoft last week revealed a new hacking group it calls Hafnium, which operates in, and is backed by, China. Hafnium used four previously unreported vulnerabilities — or zero-days — to break into at least tens of thousands of organizations running vulnerable Microsoft Exchange email servers and steal email mailboxes and address books.

It's not clear what Hafnium's motives are. Some liken the activity to espionage — a nation-state gathering intelligence or industrial secrets from larger corporations and governments.

But what makes this particular hacking campaign so damaging is not only the ease with which the flaws can be exploited, but also how many — and how widespread — the victims are.

Security experts say the hackers automated their attacks by scanning the internet for vulnerable servers, hitting a broad range of targets and industries — law firms and policy think tanks, but also defense contractors and infectious disease researchers. Schools, religious institutions and local governments are among the victims running vulnerable Exchange email servers and caught up by the Hafnium attacks.

While Microsoft has published patches, the U.S. federal cybersecurity advisory agency CISA said the patches only fix the vulnerabilities — and won't close any backdoors left behind by the hackers.

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There is little doubt that larger, well-resourced organizations have a better shot at investigating if their systems were compromised, allowing those victims to prevent further infections, like destructive malware or ransomware.

But that leaves the smaller, rural victims largely on their own to investigate if their networks were breached.

"The types of victims we have seen are quite diverse, many of whom outsource technical support to local IT providers whose expertise is in deploying and managing IT systems, not responding to cyber threats," said Matthew Meltzer, a security analyst at Volexity, a cybersecurity firm that helped to identify Hafnium.

Without the budget for cybersecurity, victims can always assume they are compromised — but that doesn't equate to knowing what to do next. Patching the flaws is just one part of the recovery effort. Cleaning up after the hackers will be the most challenging part for smaller businesses that may lack the cybersecurity expertise.

It's also a race against the clock to prevent other malicious hackers from discovering or using the same vulnerabilities to spread ransomware or launch destructive attacks. Both Red Canary and Huntress said they believe hacking groups beyond Hafnium are exploiting the same vulnerabilities. ESET said at least 10 groups were also exploiting the same server flaws.

Katie Nickels, director of intelligence at threat detection firm Red Canary, said there is "clearly widespread activity" exploiting these Exchange server vulnerabilities, but that the number of servers exploited further has been fewer.

"Cleaning up the initial web shells will be much easier for the average IT administrator than it would be to investigate follow-on activity," said Nickels.

Microsoft has published guidance on what administrators can do, and CISA has both advice and a tool that helps to search server logs for evidence of a compromise. And in a rare statement, the White House's National Security Council warned that patching alone "is not remediation," and urged businesses to "take immediate measures."

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How that advice trickles down to smaller businesses will be watched carefully.

Cybersecurity expert Runa Sandvik said many victims, including the mom-and-pop shops, may not even know they are affected, and even if they realize they are, they'll need step-by-step guidance on what to do next.

"Defending against a threat like this is one thing, but investigating a potential breach and evicting the actor is a larger challenge," said Sandvik. "Companies have people who can install patches — that’s the first step — but figuring out if you’ve been breached requires time, tools and logs."

Security experts say Hafnium primarily targets U.S. businesses, but that the attacks are global. Europe's banking authority is one of the largest organizations to confirm its Exchange email servers were compromised by the attack.

Norway's national security authority said that it has "already seen exploitation of these vulnerabilities" in the country and that it would scan for vulnerable servers across Norway's internet space to notify their owners. Slovenia's cybersecurity response unit, known as SI-CERT, said in a tweet that it too had notified potential victims in its internet space.

Sandvik said the U.S. government and private sector could do more to better coordinate the response, given the broad reach into U.S. businesses. CISA proposed new powers in 2019 to allow the agency to subpoena internet providers to identify the owners of vulnerable and unpatched systems. The agency just received those new powers in the government's annual defense bill in December.

"Someone needs to own it," said Sandvik.

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