Defense officials confirmed that the IDF is aware of the problem. They said that at one point, the government had even considered making the clans to which the armed men belong responsible for distributing aid to Gaza’s residents, even though some of the clans’ members are involved in terrorism, and some are even affiliated with extremist organizations like the Islamic State.
Source on ISIS being behind the looting?
Every source I’ve seen suggests it’s home grown Palestinian gangsters lead by Abu Shabab.
https://www.haaretz.com/israel-news/2024-11-11/ty-article/.premium/the-idf-is-allowing-gaza-gangs-to-loot-aid-trucks-and-extort-protection-fees-from-drivers/00000193-17fb-d50e-a3db-57ff16af0000
https://archive.md/t28IY
So source: the IDF