Uniquely..., Indonesia has ethnic based crime group and underworld gangs.
I don't mean to offence or humiliate certain ethnic groups here..., but it's there.
For example in Jakarta there is rivalry between Madurese and -so called- Betawi thugs and underworld men to "own" certain dark areas, especially gambling and prostitution districs.
You know..., rebutan lapak-lapak judi and setoran dari germo dan pelacur.
Preman (thugs) from Palembang, Medan (Batak), and Banten are well known as violent robbers, especially in busses, terminals, taxis, and other public transportation. While thugs from Java often specialized as pickpocket, penipu (cheating people), or just ordinary thief (oldfashioned "maling"). While eastern Indonesian ethnics such as Ambonese, Timorese, and Floresian sometimes work as "security" for bars, billiard pools or other "nightlifes" spots, and sometimes used as debt collectors to terrorizing and torture "naughty" debitors.
There's also famous (but hush-hush

) Chinese descent godfather and gangsters. The crime field of certain Chinese criminals vary from corruptors to cold blooded killers (like Gunawan that still at large...

).
But sometimes...., certain "dark" military officers play in shadows..., especially politics.

You know....., oknum aparat polisi and militer that play dirty too.
Oh no..., I said too much.....
He..he..