After a tantalizing two weeks involving the arrest of 10 Russian intelligence agents in three U.S. cities, the anticlimactic denouement came yesterday with a spy-swap deal between the United States and Russia in which the accused spies will go free after spending just 10 days in jail. It may seem odd to end a 10-year investigation on suspected foreign agents this way, even if their intelligence amounted to Google searches and pool-party gossip. But given the way the FBI normally deals with spies, putting them in jail probably wasn't its only goal in the first place.
Relative to the large number of foreign spies tracked and monitored by the FBI, very few are brought to light through criminal prosecution. This is partly due to the limited number of laws against spying. Apart from the federal espionage statute, which requires prosecutors to prove the intentional passage of classified information, the only law against spies (and the one under which the latest Russian agents have been charged) is the Foreign Agent Registration Act. FARA requires anyone acting on behalf of a foreign government to register as a foreign agent with the Department of Justice. If you're caught breaking the law, the penalty is fairly weak: five years in prison. Only four criminal cases have been brought under the statute since 1966. The dearth of spies prosecuted under either the espionage statute or FARA reflects the FBI's reluctance to lay all of its cards on the table, which is what it generally has to do at trial in a criminal case.
In the game of spy vs. spy, the FBI's strongest weapon is keeping its adversary from knowing what it knows. The investigation into the 10 Russian spies shows that Russia's foreign intelligence service, the Sluzhba Vneshney Razvedki (successor to the KGB) apparently felt confident that it was operating undetected. Working under this assumption, the SVR unwittingly enabled the FBI to collect a steady stream of information on the SVR's agents, contacts, interests, and capabilities. By staying behind the scenes, the FBI ensured that the SVR was giving up all these goodies for almost 10 years.
Criminal cases, by contrast, are public, and unless a judge chooses to seal sensitive evidence, they require the government to present exactly what it knows. The criminal complaint against the Russian spies, many note, reads like a Cold War spy thriller, complete with secret rendezvous, false identities, and messages written in invisible ink. For the Russians, though, it should read more like a McKinsey report for how the SVR can improve its game. The complaint names—or, in spytalk, "burns"—the specific FBI agents who conducted this investigation. While FBI counterintelligence agents normally operate overtly—meaning that they don't have to hide the fact that they are with the FBI—they generally do not reveal the country whose agents they are targeting. Now that the complaint has revealed the identities of the SVR's adversaries, the Russian intelligence service can keep an eye out for the specific agents working against them in the United States. (The FBI could, of course, counter-counter-counter by moving these agents to a different target, but given their institutional knowledge and Russian expertise, that would be a loss for our intelligence capabilities).
More significantly, the complaint reveals what the FBI knew about the SVR's tactics and tradecraft. For instance, the FBI learned that in addition to old-school techniques like the "brush pass" (casually exchanging bags between two people while passing), the Russians were using Web imaging encryption software to encode secret messages into ordinary pictures on the Internet, a technique known as steganography. Discovering and decrypting this software allowed the FBI to analyze more than 100 coded text files related to this investigation and likely more communications related to other classified investigations. Now that the SVR knows we know, it will no doubt improve its codes, or abandon this technique entirely, drying up a potential intelligence source for the FBI. (Other, less sophisticated notes to self for future SVR spies include not using bright orange bags, mentioning "Siberia" in conversations, or throwing cell phone receipts into the garbage.)
Despite the information it reveals to the other side, criminal prosecution has been necessary and inevitable to stop exchanges of highly classified information such as the secrets passed on to the Russians by former FBI agent Robert Hansen. Still, even that case revealed more about the FBI's own shortcomings than about the Russians. After all, as a Russian counterintelligence agent himself, Hansen had the knowledge and training to outmaneuver the traditional techniques of his FBI colleagues for almost two decades. The investigation into his activities gave the FBI guidance on internal security loopholes that needed to be fixed. The FBI adapted accordingly, enhancing its computer security and requiring regular financial disclosures and polygraphs of its agents.
Trading the Russian spies makes sense to ensure that the FBI doesn't leak any more than it already has. But in light of what the FBI lost to the Russians with Hansen, officials must have thought carefully before making the decision to arrest the spies at all. The FBI's Russian counterintelligence program is the agency's oldest and the most protective of its methods and sources. Its agents were well-aware that they were killing (or at least maiming) the goose with the golden eggs by making this case public, and only an anticipated benefit would justify the injury. One possibility is that the arrests were necessary to force the SVR to shut down other activities that pose a greater threat to national security—one that the American public will never know about. Another may be that these arrests will serve to as an example to more important spies on the FBI's radar and help persuade them to work for us as double agents rather than risk being sent home, or to jail. What is certain is that the FBI must have thought it had more to gain than lose—otherwise, the normal course of business would have been to let the spies continue their charade, at the Russians' expense.