In December 2018, researchers at Google detected a group of hackers with their sights set on Microsoft’s Internet Explorer. Even though new development was shut down two years earlier, it’s such a common browser that if you can find a way to hack it, you’ve got a potential open door to billions of computers.
The hackers were hunting for, and finding, previously unknown flaws, known as zero-day vulnerabilities.
Soon after they were spotted, the researchers saw one exploit being used in the wild. Microsoft issued a patch and fixed the flaw, sort of. In September 2019, another similar vulnerability was found being exploited by the same hacking group.
More discoveries in November 2019, January 2020, and April 2020 added up to at least five zero-day vulnerabilities being exploited from the same bug class in short order. Microsoft issued multiple security updates: some failed to actually fix the vulnerability being targeted, while others required only slight changes that required just a line or two to change in the hacker’s code to make the exploit work again.
“Once you understand a single one of those bugs, you could then just change a few lines and continue to have working zero-days.”
This saga is emblematic of a much bigger problem in cybersecurity, according to new research from Maddie Stone, a security researcher at Google: that it’s far too easy for hackers to keep exploiting insidious zero-days because companies are not doing a good job of permanently shutting down flaws and loopholes.
The research by Stone, who is part of a Google security team known as Project Zero, spotlights multiple examples of this in action, including problems that Google itself has had with its popular Chrome browser.
“What we saw cuts across the industry: Incomplete patches are making it easier for attackers to exploit users with zero-days,” Stone said on Tuesday at the security conference Enigma. “We’re not requiring attackers to come up with all new bug classes, develop brand new exploitation, look at code that has never been researched before. We’re allowing the reuse of lots of different vulnerabilities that we previously knew about.”
Low hanging fruit
Project Zero operates inside Google as a unique and sometimes controversial team that is dedicated entirely to hunting the enigmatic zero-day flaws. These bugs are coveted by hackers of all stripes, and more highly prized than ever before—not necessarily because they are getting harder to develop, but because, in our hyperconnected world, they’re more powerful.
Over its six-year lifespan, Google’s team has publicly tracked over 150 major zero-day bugs, and in 2020 Stone’s team documented 24 zero-days that were being exploited—a quarter of which were extremely similar to previously disclosed vulnerabilities. Three were incompletely patched, which meant that it took just a few tweaks to the hacker’s code for the attack to continue working. Many such attacks, she says, involve basic mistakes and “low hanging fruit.”