(CNN) CIA officers working overseas used to expect to be followed after hours by adversarial spies hoping to find their sources.

But now, foreign spies often don't need to bother because technology can do it for them, said Dawn Meyerriecks, deputy director of the CIA's science and technology division.

Digital surveillance, including closed-circuit television and wireless infrastructure, in about 30 countries is so good that physical tracking is no longer necessary, Meyerriecks told the audience at an intelligence conference in Tampa, Florida, on Sunday.

"Singapore's been doing it for years," she told CNN following her keynote speech on Sunday morning at the 2018 GEOINT Symposium, hosted by the United States Geospatial Intelligence Foundation. Meyerriecks did not elaborate with further examples.

But the CIA is spying back, she said. As of six months ago, the agency has been pursuing nearly 140 artificial intelligence projects.

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