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Brussels Attacks: Authorities Try to Keep Cell Network Up Under Strain

Belgian police have in recent days made progress in tracking terrorists' telephonic metadata.

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Belgian authorities have a simple message for anxious citizens turning to their cell phones to check in on loved ones: don’t.

In the aftermath of Tuesday’s terrorist strikes, so many people rushed to call friends and relatives that cell-phone networks in the Belgian capital went down, according to the country’s deputy prime minister, Alexander De Croo. Social media users around the capital also reported spotty service.

De Croo urged Brussels residents to instead use data-based messaging services like Twitter, WhatsApp, and Facebook to check in with friends and family. De Croo added that Internet provider Telenet had opened its wireless hotspots in Brussels to the public.

That appeal may be linked with what is an active police investigation that in recent days has made extensive use of cell-phone contacts to track terrorist suspects. On Friday, Belgian police arrested Salah Abdeslam, who is thought to be the only operative from November’s Paris attacks to still be alive. Investigators reportedly found his hide-out with the help of a cell-phone number recovered during a raid last week that left an Algerian militant dead.

During that raid, police found a fingerprint belonging to Abdeslam, which helped them determine that he was still alive. A cell-phone number recovered from the apartment was used to determine his location.

In modern police investigations, cell phones can be incredibly powerful tools. Cell-phone companies can use the tower to which a phone connects to determine a person’s rough location. Smart phones equipped with GPS technology can determine a person’s location down to a few feet. Through co-location techniques — which involve examining which phones are near one another — police can establish who met with whom and when. Call records can help authorities find and disrupt terrorist networks. Wiretaps can give police a window into operational planning.

But Islamic State operatives in Europe have gone to pains to secure their communications against exploitation by police and intelligence services. They reportedly rely extensively on burner phones — devices that are used once and then quickly discarded. The Islamic State also encourages and trains their members in the use of encrypted communications tools and techniques to mask their location.

Belgian police have clearly struggled to adapt to the Islamic State’s operational techniques, but if Friday’s arrest of Abdeslam is any indication, they have begun to make some progress in tracking terrorist networks. They weren’t, however, able to use that information to prevent Tuesday’s strikes.

And that’s likely one reason why De Croo would like cell networks to stay up on Tuesday. Police will be mining them for any possible contacts between terrorist groups in the hope of preventing a new attack.

Photo credit: KENZO TRIBOUILLARD/AFP/Getty Images

Elias Groll is a staff writer at Foreign Policy covering cyberspace, its conflicts, and controversies. @eliasgroll

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