The first real-world effects of processor vulnerabilities Meltdown and Spectre are beginning to show, due to fixes for the two megabugs which have the side-effect of slowing down cloud services worldwide.

Online video game Fortnite is one of the worst hit, with the game’s creators attributing login issues and service instability to a 30 percentage point spike in processor use that occurred when the company installed the patches.

Q&A What are Meltdown and Spectre? Show Hide Meltdown and Spectre are the names of two serious security flaws that have been found within computer processors. They could allow hackers to steal sensitive data without users knowing, one of them – Meltdown – affecting chips made as far back as 1995. Meltdown is a security flaw that could allow hackers to bypass the hardware barrier between applications run by users and the computer’s core memory, which is normally highly protected.

Spectre is slightly different. It potentially allows hackers to trick otherwise error-free applications into giving up secret information. Practically every computing device affected by Spectre, including laptops, desktops, tablets, smartphones and even cloud computing systems. A few lower power devices, such as certain Internet of Things gadgets, are unaffected.

Read a full explainer on Spectre and Meltdown processor security flaws

“All of our cloud services are affected by updates required to mitigate the Meltdown vulnerability,” said a spokesperson for Fortnite’s publisher, Epic Games. “We heavily rely on cloud services to run our back-end and we may experience further service issues due to ongoing updates. We are working with our cloud service providers to prevent further issues and will do everything we can to mitigate and resolve any issues that arise as quickly as possible.”

Users of AWS, Amazon’s cloud services division, have seen similar spikes in CPU usage following the patches. One developer reported processor utilisation tripling, while a number of others took to support forums to complain of degraded performance and forced reboots immediately after the system maintenance.

Individual users may also see slowdowns following the installation of the fixes, but only if they carry out particular types of intensive use: casual users and hardcore gamers are unlikely to see any reduction in efficiency locally, since they don’t perform the sorts of actions which the patches impact.

Security experts are warning users to apply the software patches regardless of whether or not they expect to suffer from system slowdown, since the downsides of running a vulnerable computer are much worse than simple sluggishness.

Spectre and Meltdown expose users with affected processors – which comprise a substantial proportion of those on the market – to data theft through attacks as simple as malicious advertisements.