What type of antivirus software is best for preventing slowdowns?

The best type of antivirus software for preventing slowdowns is one that offers real-time protection against malware and other malicious threats. It should also be able to detect and remove existing infections, as well as provide regular updates to keep its virus definitions up to date. Additionally, an antivirus program should have a small system footprint so it does not take up too much system resources, which can cause performance issues.