Anal sex is not safe
When you have anal sex with someone who has a STD you run the risk of getting infected.
When a finger or instrument is inserted the rectum can get damaged if it’s not done carefully.

How to protect yourself?
With rimming you should always use a dental dam or a condom sliced at the side. Not only to protect your self against STD’s, like hepatitis, herpes, syphilis and chlamydia, but also against intestinal parasites and bacterial infections. Put some water-based lubricant around the anus and at the outside of the dental dam.
With anal intercourse you have to use a condom that is made for this purpose. It’s stronger than condoms made for vaginal intercourse.
When you use the anal toys of someone else always cover them with a condom first.
When you have anal intercourse always use lots of water-based lubricant. It feels better and it decreases the risk of the condom tearing.