The extremists used a complex system to monitor movements through the Syrian border town of Tel Abyad before the militants were driven out by Kurds over the summer.
Kurdish commanders found a series of passenger manifests dating from late 2014 to early 2015 showing how buses had passed through the town.
According to the Guardian, which obtained the documents, the papers show how the names, birth dates and identification numbers of passengers were taken down by ISIS operatives.
The seven papers were said to be marked up with stamps for the terror group’s ‘department of transport’ and ‘department of immigration’.
Many of those registered were coming from territory held by ISIS, the Guardian reports, while one document shows a group of five Tunisians coming to the area.
Read more: Daily Mail