PWO uses a publicly-available software to build its installers; and we always carefully scan and audit them prior to distribution. The installer engine uses an internal compression routine to keep the file size down, so that the installer takes up less space than PWO itself, and can be downloaded quicker as a result.
Some anti-malware software products look for suspicious behaviour from "unknown" software to determine potentially new and as-yet-unknown viruses, in order to block them as early as possible. Unfortunately, some of these products are a little paranoid and over-zealous in their protections; and treat the compression in our installer as "suspicious code", and thus try to block it even though it's actually completely safe and publicly-available code. Some products even go further, and assume that if the installer is "bad", the software it installs must also be "bad". This is actually a flaw in their own protections, and not a sign of anything wrong with PWO.
Rest assured, PWO is completely safe. As long as you download PWO via an official download link (i.e. any link listed on
https://forum.pokemon-world-online.com/index.php?pages/download-links/), you should have nothing to worry about. You can use an online tool such as
VirusTotal to double-check your download if you need extra confidence; but in general, if your anti-malware is flagging PWO as a virus, you can ignore the warning and may want to add an exception to your anti-malware to prevent future issues - or perhaps look at an alternative software with more accurate results