system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't two anti-virus protectors work together?

My new Kaspersky anti-virus program sees Windows Defender as malware. This isn't the first time I've heard of two anti-virus protectors seeing each other as threats. Why do they recognize another protection program as malware/...? What part of the program do they identify as bad, and why that part?

EDIT: Thanks everyone!
gpt
Let's say you hire two security guards to guard your bank - without telling each other. When one of them sees the other enter the bank at night, with a gun, would you be surprised if he just shoots him?

The security guards will be able to work as a team, only if they know each other and work out a way to share their duties.

Two different Anti-virus programs can play well together if they are designed to recognize each other and play well with each other. If you use two programs not originally designed to work with each other, expect problems.

As a trivial example, if one of them locks access to some system files as a matter of protection, the other can recognize that it is being blocked and will identify the blocking software as malware.