McAfee Managed Virus Scan software has a feature called "ScriptScan." The "ScriptScan" feature intercepts data that is sent to Internet Explorer, then runs it through an inefficient scanning process that utilizes 100% of the CPU. Once the scan process is completed the CPU is released and the page is then rendered. The more JavaScript that a page has, the slower the script scan process is.

The "Script Scan" feature affects Project Insight significantly because Project Insight relies on JavaScript to make the user experience richer. Other sites which use JavaScript are affected by the "ScriptScan" feature as well.

The workarounds to this problem:

1. Disable McAfee temporarily for troubleshooting
2. Disable the "ScriptScan" feature in McAfee Managed Virus Scan. Disabling the "ScriptScan" feature may make the performance return to near normal
3. McAfee has documented a workaround to whitelist specific URLs for exclusion from the ScriptScan  process. This workaround would normally be performed by internal personnel responsible for managing Windows PCs under authorization of the network security team. It requires Windows Registry modification. The instructions are located at https://kc.mcafee.com/corporate/index?page=content&id=KB65382

For more information, contact support for the steps to reproduce this problem.

Here are the steps we used to reproduce the problem:

1. Signup for McAfee Managed Virus Scan software trial
2. Wait for the email from McAfee. Login to the website from McAfee, use the email address that you signed up on the trial. Go to My Account -> Configure -> Manage Policies. Create a new policy called "Disable Script Scan". Configure the policy, turn off the "Script Scan Feature". Make sure that "unassigned" group is setup for your new policy
3. Signup for another McAfee Managed Virus Scan account. This one use the default settings so don't login to their account at all
4. Wait 24 hours for the changes in McAfee Managed Virus Scan to take place. Per McAfee the change in policy will occur within up to 24 hours
5. Run Project Insight in Firefox to get the baseline performance. Click between the "My Insight" link in the menu and the "Current Time Sheet" link to see the performance between those pages. Page refresh should be 1-2 seconds maximum on a faster (T-1 or Cable) network
6. Un-Install McAfee Managed Virus Scan or any other scanning device
   NOTE: Disabling McAfee Managed Virus Scan does NOT disable the ScriptScan Feature and therefore has no effect on the performance. You must Un-Install it completely to get a baseline of IE performance without it. The install and unistall feature is very simple and takes 5-10 minutes to perform so this should not be a problem
7. Launch IE, go to Tools -> Internet Options -> Settings. Under the section "Check for newer versions of stored pages" select "Always". Close all browsers
8. Re-Open and run IE without any Anti-Virus software installed, specifically without McAfee to get the perfomance measurements. Make sure IE performs in an equivalent manner to FireFox. Use the same test as the FireFox
9. Once you have gathered the baseline performance measurements, install the "default" trial of McAfee using the provided link from the email. Be sure to use the correct one, the one that does not have the "script scan" feature enabled
10. Close all browsers
11. Run IE, navigate to Project Insight and perform the performance test. You should see degraded performance in IE. When navigating between "My Insight" and "Current Time Sheet" the CPU will be 100% for 5-10+ seconds
12. Run Firefox and perform the same performance test. The performance should be similar to the original performance
13. Close all browsers
14. Disable McAfee virus scan
15. Re-Run the IE performance test. You should see performance return to the original baseline performance
16. Install the McAfee Managed Virus Scan that has the "Script Scan" disabled
17. Close all browsers
18. Re-Run the IE performance test. The performance should be near the original baseline performance with only slightly degraded performance
19. Disable McAfee Managed Virus Scan

For more information about McAfee Script Scan causing performance problems with IE and other applications search "McAfee Enterprise slow IE" or "McAfee script scan slow IE" on Google.