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GCHQ: A cyber-what-now? Rumours of our probe into London Stock Exchange 'cyberattack' have been greatly exaggerated

Despite 'people familiar with matter' claiming otherwise to US news

GCHQ and its cyber-defence offshoot NCSC have both denied that they are investigating a cyber-attack on the London Stock Exchange, contrary to reports.

The Wall Street Journal, normally a reliable source for news with a financial flavour, reported that British signals intelligence agency Government Communications Headquarters (GCHQ) has been looking into an August 2019 outage of the LSE, which was reported to the Financial Conduct Authority at the time.

"The incident," the newspaper claimed, "which delayed the market open by more than an hour and a half and was the worst outage in eight years, immediately triggered government cyber alert systems, according to the people familiar with the matter."

It added that GCHQ was "examining if the software code may have played a role in the outage. Officials are looking at timestamps affiliated with the code's production, which could offer clues to its origin."

Unusually, GCHQ has outright denied that it is carrying out an investigation.

The National Cyber Security Centre, GCHQ's cyber defence offshoot which normally does this sort of work during or after a cyber attack, told The Register: "The NCSC has not treated the LSE outage as a cyber security related incident and has not investigated it as such."

A spokeswoman for the eavesdropping agency added that GCHQ itself wasn't looking into the outage either.

While it is certainly possible that GCHQ and its cuddly public-facing arm are publicly denying the existence of an investigation, perhaps to keep a potential attacker in the dark, an on-the-record denial could be interpreted to point the other way.

Oddly, the WSJ doesn't include statements from GCHQ or NCSC, though it does quote an LSE spokeswoman who told the newspaper the outage was caused by a "technical software configuration issue following an upgrade of functionality." She added that the LSE "has thoroughly investigated the root cause of the issue to mitigate against any future incidents."

The London Stock Exchange itself – the largest in Europe, with thousands of companies from around the world listed – is one of the critical institutions that keeps London as one of the world's pre-eminent places for the finance industry. Outages can cause predictable levels of trouble, as we reported when one such outage happened a decade ago.

With the current Middle East situation seeming precarious following the US assassination of an Iranian general at Baghdad airport, GCHQ may have other things on its corporate mind. ®

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