In a rare public speech on Wednesday, General McCallum said it made sense why, in the aftermath of the 9/11 attacks, Western spy services dedicated unprecedented attention and resources to countering terrorist threats. Efforts during these two decades have concentrated on preventing attacks by religious extremists, both domestically and abroad. General McCallum went on to say that, in light of the ongoing instability in Afghanistan, Syria and elsewhere, religious extremism will continue to require both attention and resources by Western spy agencies.

But he added that, even though counter-terrorism remains MI5’s primary task, the agency recognizes the need to “refocus attention” to threats from state actors. The attention given in the past two decades to non-state groups has allowed countries like Russia, China and Iran to develop “a growing assertiveness” in the areas of covert operations, said General McCallum. As a result, their activities in the fields of espionage, sabotage, and even assassinations, have become “increasingly daring” and threatening.

Spies working for foreign countries have killed targets, stolen sensitive technology, and tried to recruit public figures and other key individuals through blackmail. They have also attacked telecommunications infrastructure and have perfected a host of methods for launching cyber-attacks on both the public and private sectors, with potentially catastrophic consequences, he said.

The MI5 chief illustrated his statements by revealing that British counterintelligence officers have “disrupted hostile power activity” on British soil, which could otherwise have resulted in the killing of a targeted individual. He said that this operation took place after the attempted assassination of former Russian military intelligence officer Sergei Skripal in Salisbury, England, in the spring of 2018, but provided no further details.

General McCallum’s statement came as prosecutors in the United States charged four Iranian intelligence officers with participating in a plot to kidnap Masih Alinejad, an Iranian-American New York-based journalist and human-rights activist, who is known for her critical stance of the government in Tehran.