By default the Companyweb is designed to block the uploading of files of a certain type. You can easily change this, but be warned, this setting is a server level setting and once you change it, ANY site or subsite you create on your server will allow these types of attachments. You need to consider Antivirus software specifically for sharepoint. This is due to the fact that the data is stored inside SQL databases and the standard AV software on the market does not scan INSIDE the database.
Now – on with changing the setting…Logon to the server at the consoleRun the Sharepoint Administrator program – Start >Programs >Administrative Tools> Microsoft Sharepoint AdministratorSelect the option called “Manage blocked file types” under Security Configuration.Delete the defaults or just the specific file type from here.Click OK to save the changes and your done.