In addition to detecting illegal transmissions, the Iraqis also have jamming equipment available for making sure those electronic messages don't get through. Iraq bought a lot of jamming and electronic warfare equipment from the Russians in the 1980s. After the 1991 Gulf War, Iraq has evaded the arms embargo by smuggling in more electronic warfare equipment. This has brought in additional Russian equipment, as Eastern European nations who inherited a lot of that stuff when the Soviet Union broke up were eager to sell to Iraq for cash.
Over the last two decades, Iraq had bought billions of dollars worth of computers, radios and electronic monitoring equipment. Most of this gear is not considered military equipment, but the Iraqis have fashioned it into an efficient monitoring system. With antennae and other detection equipment stationed all over Iraq, the Iraqis constantly listen for any transmissions that are not supposed to be there. This is in addition to the monitoring on the telephone system and This is another reason why there has not been a successful uprising against Saddam, as it's very difficult to use communications for anything the government doesn't approve up. To make sure the monitoring system works, there are multiple organizations running these systems. If one organization picks up a lot of suspicious transmissions that another outfit misses, questions are asked. That can often lead to fatal consequences for the crew that came up short. While brutal, this system does encourage efficiency. The special unit that monitors other electronic surveillance organizations is called Project 858. This outfit reports directly to Saddam's inner circle and is expected to promptly report any new signs dissent or resistance.