Russian government hackers seem to have figured out that sometimes the best way to hack into people's Gmail accounts is be to abuse Google's own services.
On Thursday, researchers exposed a massive Russian espionage and disinformation campaign using emails designed to trick users into giving up their passwords, a technique that's known as phishing. The hackers targeted more than 200 victims, including, among others, journalists and activists critical of the Russian government, as well as people affiliated with the Ukrainian military, and high-ranking officials in energy companies around the world, according to a new report.
Read more: Would You Click on These Fake Gmail Alerts?
Researchers at the Citizen Lab, a digital rights research group at the University of Toronto's Munk School of Global Affairs, were able to identify all these victims following clues left in two phishing emails sent to David Satter, an American journalist and academic who's written Soviet and modern Russia, and who has been banned from the country in 2014.
On October 7, Satter received a phishing email designed to look like it was coming from Google, claiming someone had stolen his password and that he should change it right away.
As with seen with other phishing attacks targeting people affiliated with the Hillary Clinton campaign that led to the DNC leaks of last year, the email, however, didn't come from Google. It was actually from a group of hackers known as Fancy Bear, or APT28, whom many believe work for Russia's military intelligence, the GRU.
The "Change Password" button linked to a short URL from the Tiny.cc link shortener service, a Bitly competitor. But the hackers cleverly disguised it as a legitimate link by using Google's Accelerated Mobile Pages, or AMP. This is a service hosted by the internet giant that was originally designed to speed up web pages on mobile, especially for publishers. In practice, it works by creating a copy of a website's page on Google's servers, but it also acts as an open redirect.
According to Citizen Lab researchers, the hackers used Google AMP to trick the targets into thinking the email really came from Google.
"It's a percentage game, you may not get every person you phish but you'll get a percentage," John Scott-Railton, a senior researcher at Citizen Lab, told Motherboard.
So if the victim had quickly hovered over the button to inspect the link, they would have seen a URL that starts with google.com/amp, which seems safe, and it's followed by a Tiny.cc URL, which the user might not have noticed. (For example: https://www.google[.]com/amp/tiny.cc/63q6iy)
Using Google's own redirect service was also perhaps also a way to get the phishing email past Gmail's automated filters against spam and malicious messages.
"It's a percentage game, you may not get every person you phish but you'll get a percentage."
According to Citizen Lab, who doesn't directly point the finger at Fancy Bear, the email was actually sent by annaablony[@]mail.com. That address was used in 2015 by Fancy Bear to register a domain, according to security firm ThreatConnect. And another domain used in the October attacks exposed by Citizen Lab was also previously linked to Fancy Bear, according to SecureWorks, which tracked the phishing campaign against the DNC and the Clinton campaign.
Curiously, the email targeting Satter came just a few days before Google warned some Russian journalists and activists that "government-backed attackers" were trying to hack them using malicious Tiny.cc links.
Now we know that in October of 2016, when the hackers targeted Satter and at least 200 other people, the trick of using Google AMP was working, and Google hadn't blocked it. Google has previously dismissed concerns about open redirectors, arguing that "a small number of properly monitored redirectors offers fairly clear benefits and poses very little practical risk."
On Thursday, a company spokesperson said that this is a known issue and last year some Google AMP URLs started showing a warning if the company's systems are uncertain whether the link is safe to visit, such as this.
But for some security researchers, they are dangerous.
"The AMP service's behavior as an open redirect for desktop browsers was clearly abused in this situation and is also just trivial to abuse in general," Nicholas Weaver, a senior researcher at the International Computer Science Institute at UC Berkeley, told Motherboard in an email. "There is undoubtedly some engineering tradeoff I'm not seeing that causes them to maintain it."
Google's redirectors might not be the only part of Google's infrastructure that Fancy Bear hackers have been taking advantage of. Citizen Lab researchers found a Tiny.cc URL that targeted an email address—myprimaryreger[@]gmail.com—that other security researchers suspect was used by Fancy Bear to test their own attacks.
That address had a Google Plus page filled with images that appear in real, legitimate Gmail security alerts. It's unclear what the hackers used these for, or if they used them at all. But the researchers said that perhaps the hackers were embedding them in phishing emails, and the fact that they were hosted on Google Plus perhaps helped thwart Gmail's security controls.
The Fancy Bear hackers are known to use popular services like URL shorteners in their high-profile hacking operations. And, sometimes, those URL shorteners betray them and end up revealing who they targeted.
Between March 2015 and May 2016, as part of their operation to hack Clinton's campaign chairman John Podesta, and former National Security Advisor Colin Powell, the hackers targeted more than 6,000 people with more than 19,000 phishing links. Some of those used Bitly URLs that, as it turned out, could be decoded to figure out who they were intended to.
Similarly, in this case Citizen Lab researchers were able to identify the victims by figuring out that there was a pattern behind how Tiny.cc creates short URLs. That pattern, as research fellow Adam Hulcoop explained to me, "was chronological." So, starting from the links sent to Satter, the researchers were able to guess other links created around the same time.
It's impossible to know why the hackers keep relying on services like Bitly or Tiny.cc, which end up exposing some of their operations—although months later. One explanation could be that their phishing campaigns are highly automated, given that they target thousands of people. So, as Hulcoop put it, they need a modular phishing infrastructure where every element can be modified if needed, as "an insurance policy of sorts" and they use third party services "to try and balance the need for OpSec [operational security, or the practice of keeping operations secret] with the ability to operate at scale."
"The construction of the Tiny.cc shortcodes pointing to TinyURL shortcodes, which ultimately point to phishing sites on different servers. This modularity is likely by design so that the operator can change up the individual components, servers, redirectors, etc., and only abandon the pieces that are burned," he said in an online chat. "The more layers you have, the more flexible you can be."
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