Anti-virus software makers are detecting malware that attempts to exploit the security vulnerabilities identified as Spectre and Meltdown. Since code must execute on the computer to exploit these vulnerabilities, anti-virus software is being updated to detect such malware attacks. Of course, some such malware may yet get through our defenses and could end up on machines.
My view is that for most of us, its just another form of malware. We all need to be pro-active about avoiding malware by taking appropriate steps such as installing code we know to be good, using anti-virus software, and keeping our systems generally update. Meltdown and Spectre are just two more exploits that hackers can use.