Cyber experts from military intelligence agency the GRU targeted Yulia Skripal’s email accounts as far back as 2013, according to the security chief.
A program set up in Russia in the 2000s trained personnel from “special units” in the use of chemical warfare agents, he said, including investigating how nerve agents could be administered through door handles.
In an analysis of samples taken from the home of the Skripals, the highest concentrations of toxic chemical novichok, thought to be responsible for their poisoning, was found on door handles.
Sir Mark made the claims in a letter to Nato secretary general Jens Stoltenberg.
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It followed a report by the Organisation on the Prohibition for Chemical Weapons that backed UK findings that novichok, a Soviet-era nerve agent, was responsible for the poisoning of former spy Sergei Skripal and his daughter Yulia.