Ask HN: Are most of Redis server really infected?

Keyword being "open" redis servers. Redis is not made to be run publicly accessible, and scanning the entire internet for open services is easy nowadays, so yes, if you leave your server freely accessible it probably gets compromised.

If one open redis instance is compromised, then they probably all are. Attackers scan the open internet for vulnerable hosts and then deploy their payloads to any they find.

If you go searching for open mongo databases in shodan, you’ll see the same thing. Most of them have been pwned and have a single table with instructions on where to send bitcoin to get their data back.

"Clarifications on the Incapsula Redis security report" http://antirez.com/news/118 > antirez 17 days ago

The article talks about PUBLIC or OPEN Redis instances. Redis should never be publicly visible or availbale, so the people running them are really bringing this onto themselves.