One unidentified conspirator used the cover name "Fatty"; another in the plot which Belgian authorities have said intended to target police officers, went by the handle "Big Lanky".
Among seven accused present on the first day of a terrorism trial that began in Brussels under heavy security seven weeks after suicide bombers killed 32 people in the capital was Marouan El Bali. He survived the gunfight in January 2015 when police shot dead two armed men who had returned from fighting with IS in Syria.
In summarising the case against the 16 accused, nine of whom are still at large, the judge offered details of how security services had used telephone taps to help combat a potential threat from more than 300 Belgians who have fought in Syria.
In a tapped call in November 2014 an unidentified man told another who was on a police watchlist: "I've got everything."