Hacker George Hotz has shown off his latest "custom firmware" for PS3, which reintroduces features disabled by the most recent, mandatory PS3 update.

While early April's 3.21 update - which has reportedly caused numerous system errors - removed the ability to install alternative operating systems, iPhone and PS3 hacker Hotz has come up with his own version that can run the removed OtherOS functionality.

"I would have added something showing off the new features of 3.21, but oh wait, there aren't any," he wrote on his blog.

"This can be installed without having to open up your PS3, just by restoring a custom generated PUP file, but only from 3.15 or previous. It's possible this CFW will also work on the slim to actually *enable* OtherOS; I'll know when my infectus gets here.

He also warned Sony: "Note to the people who removed OtherOS, you are potentially turning 100000+ legit users into "hackers." There was a huge(20x) traffic spike to this blog after the announcement of 3.21. If I had ads on this site I guess I'd be thanking you."

PS3 firmware 3.21 was released just months after Hotz claimed to have breached security measures on the system through the Install OtherOS feature.