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As the body of anti-virus software grows, resources are occupying more and more resources, and there are more and more "streaking" people. In fact, as long as you have good habits, pay more attention to it at ordinary times, even if you do not install anti-virus software, it is not a great threat.
But what if I suspect that the system is secure? Do I have to install anti-virus software once? In this case, the best solution is online detection, which is fast and free. Here is a list of online virus and Malware detection services, which I believe can meet your needs.
Avast-Avast's online version can detect a single file up to kb.
BitDefender-BitDefender's online version can scan the entire system and only support Internet Explorer.
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Computer Associates Malware program-Detect a single file.
Eset-Checks whether the entire system has malware.
Freedom-Detect the entire system.
Jotti's Malware Scan-Use multiple engines to scan the uploaded files at the same time.
NanoScan.com
Panda Security-Check whether there are worms, viruses, Trojans, and other malicious programs in your system.
TrendMicro-Detect viruses, spyware, and malware in the system.
VirusTotal.com-Scan a single file up to 10 MB with over 30 antivirus engines.