The British spy agency GCHQ discovered how to exploit security holes in 13 different firewall models made by Juniper Networks, a security company that revealed the existence of security holes in its products last week.

According to a secret document, titled "Assessment of intelligence opportunity – Juniper" supplied to The Intercept — a website run by lawyer Glenn Greenwald — by former NSA contractor and whistleblower Edward Snowden, the British organisation may have been helped in its endeavours by America's key spying body, the National Security Agency.

In 2013, based on documents supplied by Snowden, Greenwald revealed that the NSA was conducting mass surveillance of the US population. Several other equally disturbing stories have flowed from the collaboration between the pair since then.

The six-page document, dating from February 2011, does not establish conclusively that there is a link between the NSA, the GCHQ and the vulnerabilities that Juniper revealed last week. However it is plain that these agencies worked together to discover a means to get past the security offered by Juniper's NetScreen line of products which run an operating system known as ScreenOS.

Juniper has another line of products, including high-volume internet routers, which run an operating system known as JUNOS.

The revelations in the document come at a time when there isfrom the US government and its associated security agencies to create backdoors in encryption so that public data can be accessed as and when deemed necessary. No government agency has been able to show, however, that any act deemed to be terrorism has been carried out with the aid of encrypted messaging.

Two Juniper vulnerabilities were announced last week: one, dating back to 2012, allows access to encrypted data transmitted over VPNs. The other, which dates back to 2014, permits an attacker to remotely administer a firewall, leading to a complete compromise of the system in question.

And in the case that either loophole had been taken advantage of, there was no way to detect it, according to a statement from Juniper.

The document says: "While Juniper is not necessarily the market share leader in any one space, they are a strong competitor and technology leader across several important markets from a SIGINT perspective. Juniper is at the core of the Internet in many countries by virtue of providing the highest density routers for many years.

"Juniper’s leadership in core IP routing and the Enterprise Network Firewall and SSL VPN markets means that the SIGINT community should keep up with Juniper technology to be positioned to maintain CNE (computer network exploitation) access over time."

It also lists the products in which GCHQ has found vulnerabilities and those on which it is working: "Juniper NetScreen Firewalls models NS5gt, N25, NS50, NS500, NS204, NS208, NS5200, NS5000, SSG5, SSG20, SSG140, ISG 1000, ISG 2000. Some reverse engineering may be required depending on firmware revisions. Juniper Routers: M320 is currently being worked on and we would expect to have full support by the end of the 2010."