The application AVG Anti Virus is detecting a false positive, Stronghold Crusader 2 doesn't contain a virus. Is displayed in the image below:

Please select Ignore Threat. If this doesn't work or you want to allow Crusader access, you can do the following.

1. Open AVG.

2. Select Options.

3.Select Advanced Settings.

4. Select Update, Exceptions and 'Add Exception'

5. Browse to your Steam folder and select 'Add File'

The default location could be :

C:\Program Files (x86)\Steam\steamapps\common\Stronghold Crusader 2\bin\win32_release\Crusader2.exe

If you require further help, please following the instuctions on this webpage by AVG -