Request Filtering is a built-in security feature of IIS. Using the Request Filtering feature, one can assign maximum URL length, Query String size, content request length, and many other restrictions server-wide as well as website-wide. Deny URL Sequences element of Request Filtering helps deny access for URL sequence patterns that an attacker might try to exploit. Follow these steps to deny the URL sequence from IIS.
1. Log in to your VPS. Please refer to how to connect your VPS using RDP.
2. Open IIS Manager. Unde Connections pane, click on VPS Name.
3. Open Request Filtering as shown in the below image.
4. Move to the URL tab and click on Deny Sequence. 
5. An Add Deny Sequence dialog box will appear; enter the URL sequence you wish to block. For Example, if you want to block the common SQL Injection term 'varchar', enter the 'varchar' character sequence in the Deny Sequence box. When you wish to block entire directory access, give '..' as shown in the below image.
6. Click OK. Now, when anyone tries to enter any of the mentioned terms into your URL Sequence, they will receive the HTTP Error 404.5 – URL Sequence denied error message.
NOTE: Choose your character sequence wisely. If your site uses any of the terms that you deny, your site visitor will receive the HTTP Error 404.5.
