F5 confirms hackers stole source code, bug details in disastrous security incident – here’s everything we know so far and how to protect yourself

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Cybersecurity firm F5 has confirmed state-sponsored hackers have stolen source code and customer information following a cyber attack.

In an alert to customers, the company said threat actors maintained long-term, persistent access to its BIG-IP product development environment and engineering knowledge management systems.

As part of the attack, threat actors exfiltrated files containing some BIG-IP source code, along with information pertaining to undisclosed vulnerabilities that the company was in the process of remediating.

Notably, hackers don’t appear to have accessed data from its CRM, financial, support case management, or iHealth systems. Similarly, the company's software supply chain, including its source code and build and release pipelines, doesn't appear to have been modified.

"We have no knowledge of undisclosed critical or remote code vulnerabilities, and we are not aware of active exploitation of any undisclosed F5 vulnerabilities," F5 said in its advisory.

"We have taken extensive actions to contain the threat actor. Since beginning these activities, we have not seen any new unauthorized activity, and we believe our containment efforts have been successful."

Some files from F5's knowledge management platform contained configuration or implementation information for a small percentage of customers. The firm said it was reviewing the files and contacting affected customers.

CISA, NCSC raise alarm over F5 security incident

Security agencies have issued an alert following the disclosure, with the US Cybersecurity and Infrastructure Security Agency (CISA) and the UK’s National Cyber Security Centre (NCSC) urging organizations to remain vigilant.

In an emergency directive, CISA said the incident could enable threat actors to conduct “static and dynamic analysis for identification of logical flaws” in affected products.

"Successful exploitation of the impacted F5 products could enable a threat actor to access embedded credentials and Application Programming Interface (API) keys, move laterally within an organization’s network, exfiltrate data, and establish persistent system access,” the agency said.

“This could potentially lead to a full compromise of target information systems."

CISA has ordered federal networks to take immediate action, identifying all instances of F5 BIG-IP hardware devices and F5OS, BIG-IP TMOS, Virtual Edition, BIG-IP Next, BIG-IP IQ software, and BNK/CNF.

They must check whether physical or virtual BIG-IP devices exposed to the public internet give public access to the networked management interface.

Similarly, the agency urged organizations to apply the latest vendor updates for F5OS, BIG-IP TMOS, BIG-IQ, and BNK/CNF by 22 October, disconnect end-of-support devices, mitigate against cookie leakage, and report back on all this by 29 October.

F5 attack can’t be ignored, experts warn

Ryan Dewhurst, head of proactive threat intelligence at watchTowr, said the security incident should be taken seriously by customers and urged organizations to take immediate action.

"On October 13th, F5 quietly announced it had rotated its signing certificates and cryptographic keys, the ones used to prove that F5-produced software is legitimate and untampered. That’s not a routine update. Vendors only do that when something has gone very wrong," he said.

"Older software signed with the previous keys may now warrant closer scrutiny. For a vendor whose products sit deep in enterprise and government networks, this is a serious breach of trust," Dewhurst added.

"If those compromised keys were stolen, and F5 hasn’t ruled that out, malicious software updates signed by "F5" could be indistinguishable from the real thing."

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Emma Woollacott is a freelance journalist writing for publications including the BBC, Private Eye, Forbes, Raconteur and specialist technology titles.