Customers of the popular CloudFlare website acceleration and security service were targeted in an email attack that directed them to a fake version of the website.
Reports about spoofed CloudFlare emails that contained links to a phishing website were posted Monday on the company's support forum by customers. The rogue messages masqueraded as CloudFlare alerts about account load limits being exceeded.
CloudFlare improves website performance by caching static content, optimizing Web pages and balancing the load across its global content delivery network. The service can also block comment spam, content scraping, SQL injection, cross-site scripting, distributed denial-of-service and other forms of attacks, depending on what type of account the customer has.
In order to use the service, website owners have to first assign (delegate) their domain names to the company's name servers. CloudFlare offers free accounts and paid accounts with additional features.
Around 785,000 sites are currently configured to use CloudFlare's DNS servers, according to a report released Monday by U.K.-based Internet research and security firm Netcraft.
"While I should have found out that this is a phishing mail (it was sent to my Whois address instead of the my address at Cloudflare), it was late in the evening and I fell for it," a CloudFlare customer said Monday on the company's support forum. "Realized it within a minute, though and changed my password on the real site."
"I got this email also today, and I'm embarrassed to say I fell for it," another customer said. "I had just changed some setting in CloudFlare, so it seemed reasonable that I might have exceeded some limit. My mind was in CloudFlare-mode, so the email reached me just at the wrong time."
"This was a highly targeted attack, as the phishing message mentions the exact domain name that is associated with Cloudflare [for the targeted accounts]," Bogdan Botezatu, a senior e-threat analyst at antivirus vendor Bitdefender, said Tuesday via email.
"It appears the phisher looked up websites that pointed to CloudFlare's IP range and then sent messages to the email addresses on file in the public Whois records," Matthew Prince, CloudFlare's co-founder and CEO, said Tuesday via email. "In other words, the email addresses for the attack were from public sources, not obtained through our systems."
With access to a CloudFlare account, an attacker could redirect the associated websites to an IP address under his control, Botezatu said.
"Imagine that a specific web shop gets redirected to its identical rogue clone where users enter credit card information, delivery addresses and phone numbers for couriers' convenience," Botezatu said. "In 20 minutes, the attacker can easily collect a huge pool of data, then change the IP addresses back to the original ones. In some cases, website owners may actually not spot the problem at all."
In another scenario, an attacker could change the MX (mail exchanger) record for the domain name and route all email communication to a mail server under his control, Botezatu said.
The credit card and billing information provided by customers with paid accounts is not displayed on the website, so it was not at risk of being compromised as a result of this attack, Prince said.
"These type of phishing attacks have been common among registrars and web hosts for some time," Prince said. "It is only because of CloudFlare's increasing scale, now with more than half a million customers, that we've become an interesting target."
The company was able to determine that only around 200 customers had clicked on the rogue link in the spoofed emails before the phishing website was taken down. All of those customers had their passwords reset, Prince said.
For the past few months the company has been working on implementing a two-factor authentication feature that would prevent account abuse even when the account password is compromised, Prince said. "We plan to turn it on in the next few days. Likely tomorrow."
CloudFlare had already implemented the Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) technologies to allow email providers to verify the sender's identity and block emails that spoof CloudFlare as their source, Prince said. "We will be adding a DMARC [Domain-based Message Authentication, Reporting and Conformance] policy to further enhance this protection."