It was a while ago. And it was scummy. Probably their response to Napster or Limewire.

https://en.wikipedia.org/wiki/Sony_BMG_copy_protection_rootkit_scandal#%3A%7E%3Atext%3DIn_2005_it_was_revealed%2Cto_interfere_with_CD_copying.?wprov=sfla1

They’re probably talking about the BMG rootkit from the early 2000’s. Basically, when you inserted a Sony CD into your computer, it would automatically and silently install a rootkit on your PC, which introduced a backdoor on your PC that was being actively exploited. It was also notoriously difficult to remove, as it would reinstall itself even if you deleted every visible trace of it (and improperly installing it could disable access to your CD drive entirely.)

Then when shit hit the fan and Sony was making headlines for it, they released a “fix” for it. The fix didn’t actually remove the rootkit, and simply hid files with specific names (the rootkit files) from the users. This only introduced another vulnerability, where hackers could just name any virus the same as the rootkit, and it would automatically be hidden.

It led to several very large lawsuits and state investigations. Sony was raked over the coals by multiple state attorneys general, and the FTC even published warnings urging consumers not to buy Sony CDs.

All in the name of DRM. The rootkit was initially meant to stop you from ripping and copying the CD. Oh, and the rootkit contained sections of improperly credited open source code. So Sony stole from OSS programmers while claiming that they were trying to prevent IP theft.