The most common cause of this issue is that an InTrust site containing all computers, or perhaps all servers, in your domain (network) is part of a gathering policy that uses agents or is tied to a real-time policy that has been activated.
When running gathering jobs (with agents) or activating a real-time policy, the InTrust Server will install the agent on any machine in the site(s) specified or update the agent if it is an older version. In other words, if no agent exists, or if the existing agent is an older version, then it will make attempts to install/update. If there is a firewall in place (between the InTrust console and the agent machine) that blocks NetBIOS traffic, you will see an entry in the InTrust log about a failure when attempting to install the agent.
1. Check any gathering jobs to see whether they are set to use agents and make sure that the sites that they are trying to collect from don't contain non-necessary machines (you can use the enumeration tab - only in 9.x and newer)
2. Check any real-time policies that are active to check the sites bound to them as in step 1.
3. Right-click on each built-in site and check the 'Prohibit Agent Deployment' check box to prevent these predefined sites to get used incorrectly. When you create a new site or copy one of these sites you can uncheck this box on the copy if you want agents to get deployed.
4. Once the incorrect agents have been identified they can be uninstalled from InTrust (Configuration | InTrust Servers | IT Servername | Agents) right-click uninstall or you can read the solutions for information on uninstalling: