An intermittent outage at Cloudflare on Tuesday briefly knocked many of the Internet’s top destinations offline. Some affected Cloudflare customers were able to pivot away from the platform temporarily so that visitors could still access their websites. But security experts say doing so may have also triggered an impromptu network penetration test for organizations that have come to rely on Cloudflare to block many types of abusive and malicious traffic.
At around 6:30 EST/11:30 UTC on Nov. 18, Cloudflare’s status page acknowledged the company was experiencing “an internal service degradation.” After several hours of Cloudflare services coming back up and failing again, many websites behind Cloudflare found they could not migrate away from using the company’s services because the Cloudflare portal was unreachable and/or because they also were getting their domain name system (DNS) services from Cloudflare.
However, some customers did manage to pivot their domains away from Cloudflare during the outage. And many of those organizations probably need to take a closer look at their web application firewall (WAF) logs during that time, said Aaron Turner, a faculty member at IANS Research.
Turner said Cloudflare’s WAF does a good job filtering out malicious traffic that matches any one of the top ten types of application-layer attacks, including credential stuffing, cross-site scripting, SQL injection, bot attacks and API abuse. But he said this outage might be a good opportunity for Cloudflare customers to better understand how their own app and website defenses may be failing without Cloudflare’s help.
“Your developers could have been lazy in the past for SQL injection because Cloudflare stopped that stuff at the edge,” Turner said. “Maybe you didn’t have the best security QA [quality assurance] for certain things because Cloudflare was the control layer to compensate for that.”
Turner said one company he’s working with saw a huge increase in log volume and they are still trying to figure out what was “legit malicious” versus just noise.
“It looks like there was about an eight hour window when several high-profile sites decided to bypass Cloudflare for the sake of availability,” Turner said. “Many companies have essentially relied on Cloudflare for the OWASP Top Ten [web application vulnerabilities] and a whole range of bot blocking. How much badness could have happened in that window? Any organization that made that decision needs to look closely at any exposed infrastructure to see if they have someone persisting after they’ve switched back to Cloudflare protections.”
Turner said some cybercrime groups likely noticed when an online merchant they normally stalk stopped using Cloudflare’s services during the outage.
“Let’s say you were an attacker, trying to grind your way into a target, but you felt that Cloudflare was in the way in the past,” he said. “Then you see through DNS changes that the target has eliminated Cloudflare from their web stack due to the outage. You’re now going to launch a whole bunch of new attacks because the protective layer is no longer in place.”
Nicole Scott, senior product marketing manager at the McLean, Va. based Replica Cyber, called yesterday’s outage “a free tabletop exercise, whether you meant to run one or not.”
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