There is no virus or other malware in the client. It's a false flag. This is a known issue, not just with MapleRoyals, but with all private MapleStory server clients (aka, the software you install to play). What happens is that when the private server programmers modify the client to redirect to their servers instead of the addresses of the official MapleStory servers (at the time that version of the client was released), it causes most antivirus/anti-malware software to false flag the client as a certain variant of a trojan. What you need to do is tell your antivirus software to not scan the client. You can do so by setting up the client's files as exceptions, so that they will not be scanned (how to do this varies depending on the software). Also, since the antivirus technically blocked the install from completing, I would advise uninstalling and reinstalling the game, to avoid complications from an incomplete installation. But only do this after setting up an exception for the installer that you download, and, if possible, temporarily disabling the Real-Time Protection of your antivirus, only turning it back on after you set up additional exceptions for all of the game's files. Again, your success in solving the issue really depends on whether or not you can get your antivirus to not scan the MapleRoyals files long enough for you to give the antivirus explicit instructions to not scan the files. With Windows 7 + Avira Antivirus (what I have), this is easy. If you have Windows 10, you might have a rough time (if you disable your antivirus in 10, Windows Defender automatically turns on to protect you, so you have to figure out how to shut that off too).
