Schneier on Security

An Example of Cell Phone Metadata Forensic Surveillance

In this long article on the 2005 assassination of Rafik Hariri in Beirut, there’s a detailed section on what the investigators were able to learn from the cell phone metadata:

At Eid’s request, a judge ordered Lebanon’s two cellphone companies, Alfa and MTC Touch, to produce records of calls and text messages in Lebanon in the four months before the bombing. Eid then studied the records in secret for months. He focused on the phone records of Hariri and his entourage, looking at whom they called, where they went, whom they met and when. He also followed where Adass, the supposed suicide bomber, spent time before he disappeared. He looked at all the calls that took place along the route taken by Hariri’s entourage on the day of the assassination. Always he looked for cause and effect. How did one call lead to the next? “He was brilliant, just brilliant,” the senior U.N. investigator told me. “He himself, on his own, developed a simple but amazingly efficient program to set about mining this massive bank of data.”

The simple algorithm quickly revealed a peculiar pattern. In October 2004, just after Hariri resigned, a certain cluster of cellphones began following him and his now-reduced motorcade wherever they went. These phones stayed close day and night, until the day of the bombing -­ when nearly all 63 phones in the group immediately went dark and never worked again.

[…]

The investigators now turned their full attention to the cellphone records. Building on Eid’s work, they determined that the assassins worked in groups, each with a leader and each adhering to specific procedures. Everyone in the group called the leader, and he called everyone in the group, but the lower-level operatives never called one another.

The investigators gave each group a color. The green group consisted of 18 Alfa phones, purchased with fake identification from two shops in South Beirut in July and August 2004. The purpose of the fake IDs was not to defraud Alfa out of payment; every month from September 2004 to May 2005, someone went to an Alfa office and paid all 18 bills in cash, without leaving any clue to his identity. The total phone bill for the green network, including activation fees, was $7,375 ­—a prodigious amount, considering that 15 of the green group’s 18 phones went almost entirely unused.

The first spike in call activity occurred in September 2004, immediately after Hariri announced his resignation. The investigators contend that the green group was at the center of the conspiracy. The phone number 3140023 belonged to the top leader, and the numbers 3159300 and 3150071 belonged to his two deputies. (He called them and they called him, but with those phones, they never called each other.) The two deputies carried phones belonging to other groups, through which they passed on instructions to the other participants in the operation. When a member of one group would call a group leader, the group leader would often follow up by switching to a green phone and calling the supreme leader, who was nearly always in South Beirut, where Hezbollah keeps its headquarters.

On Oct. 20, 2004, the day Hariri left office and his security detail was significantly reduced, the blue group went into operation. It originally worked according to the same rules as the green group, but its active membership increased from three phones to 15, with seven connected to Alfa and eight to MTC Touch. All of the blue phones were prepaid. Some were acquired as early as 2003 and had seen little or no use. The people who bought them also gave false identification, and again money seemed to be in plentiful supply. The minutes that expired each month went largely unused, but the phones were loaded again and again. When the blue group went dark, the phones still had unused minutes worth $4,287.

The prosecutors say the blue group followed Hariri’s movements. On the morning of Oct. 20, its members were already deployed around Quraitem Palace. At 10:30 a.m., Hariri set out toward Parliament and then to the presidential palace, where Lahoud was waiting to receive his resignation. The cell towers picked up the blue group’s members moving with him and calling their chief. From then on, the blue phones trailed Hariri nearly everywhere—­ to Parliament, to meetings with political leaders, to long lunches at the Saint-Georges Yacht Club & Marina. When Hariri was at his home, so were they. When he flew abroad, they moved with him to the airport and then stopped operating until he returned, when they would pick up the trail again.

Eventually, the yellow group was added….

There’s a lot more. It’s section 6 of the article.

See also this example.

Posted on May 6, 2015 at 7:09 AM • View Comments