Counterintelligence officials at the CIA’s headquarters in Langley, Va., have dispatched a cable to officers around the world cautioning them to take greater care in handling human sources, who are at risk of being captured or killed by rival intelligence services, according to people familiar with the matter.

The cable reflected a general concern among the agency’s leadership that its operations officers should pay more attention to protecting their agents, while also recognizing that they have to aggressively recruit spies and informants to perform their intelligence-collection mission, according to the people who spoke on the condition of anonymity to describe a sensitive matter.

Such notices to the field — known as worldwide stations and bases cables (WWSB) — are routine, former officials said. People familiar with the recent cable said it wasn’t prompted by any new penetration of a spy network. But, they added, the cable underscored concerns that CIA officers may be putting recruitment ahead of basic source-protection techniques.

Historic Pakistani success in identifying people working for the CIA was a driving force behind the cable, the people familiar with the matter said.

The CIA is under renewed pressure to recruit and maintain effective spy networks in Pakistan, following the U.S. withdrawal from neighboring Afghanistan and the country’s takeover by the Taliban. Maintaining reliable human sources will be crucial to the Biden administration’s plans to keep tabs on terrorist threats without a military presence on the ground, former officials said.

The CIA cable was first reported by the New York Times.

“These go out every two or three years on counterintelligence concerns. They’re not unusual but are still important reminders to officers to tighten up on tradecraft,” said Thad Troy, a former CIA operations officer who served as a chief of station in several European capitals. Troy said he had not seen the recent cable.

In an unusually revealing detail, the cable noted the number of agents killed by foreign intelligence services. That level of specificity might ordinarily be excluded from a cable that is widely disseminated, as this one was, but it was included to get the attention of CIA officers, who might otherwise regard the bulletin as a routine advisory, people familiar with the message said.

When asked about the cable, a CIA spokeswoman declined to comment.

The CIA has suffered some disastrous penetrations of its spy networks in recent years. In 2011, the agency launched a mole-hunt after an informant in China told his American handlers that everyone he knew who was helping the U.S. government had been discovered by Chinese authorities, who then forced the agents to work for them.

CIA assets in Iran were also identified and arrested in another penetration around the same time.

In both instances, former officials said that agents were probably discovered because of a breach in the CIA’s covert communications system, which it used to secretly communicate with agents in the field.

By invoking previous failures, the cable was probably meant to admonish current officers not to repeat past mistakes.

“If this is being sent to the workforce [rather than a particular CIA station], the message is, ‘Hey, people, let’s be careful,” said Daniel Hoffman, a former intelligence officer who held senior positions overseas and at headquarters.

Hoffman, who hasn’t seen the cable, said that if the agency wanted to send a more urgent message about an active counterintelligence problem — such as a particular group of sources being compromised — it would handle the matter in a more discreet message to the officers concerned.