GeSWall (GentleSecurityWall) is a cross between an isolator, like Sandboxie, and a Host Intrusion Prevention System (HIPS). For Windows 2000, XP, 2003, Vista, and Windows 7, it sits quietly in the background until an application exhibits suspicious behaviour. GeSWall automatically isolates certain applications (browsers, PDF viewers and file archivers) as well as files, registry keys, processes made by those applications. The generic rules for an isolated application are that the application:

1. Can read but cannot modify trusted resources.
2. Cannot read or modify confidential resources.
3. May create new untrusted resources, e.g. files.
4. May read or modify untrusted resources.

Known applications also have preconfigured rules so those applications can run properly.
In effect, files which you download will not be able to access critical areas on your computer, similar to a Limited User Account. So any malware which you inadverdently download cannot execute and damage your computer. GeSWall also allows for detailed customization where you can configure the restrictions of untrusted applications. A user at Wilders Security Forum has some interesting configuration tips for Internet Explorer 8.
Just like Sandboxie, updating applications is a problem and you need to open an un-isolated browser. The good news however is that updating add-ons/widgets and bookmarks are no problem in GeSWall .

GeSWall also does not fully track files which are saved, which means if you move an untrusted file to another partition, GeSWall will not be restricting the new file. This is not a problem with computer that have one partition. Also, when I browsed to some sites that require Javascript my browser would sometimes freeze, seemingly randomly. This was solved by opening GeSWall and lowering the security level to low. My computer felt a bit more sluggish running GeSWall compared to Sandboxie.

Overall, GeSWall provides excellent security, and is a worthy alternative to Sandboxie. Since GeSWall doesn’t use a real-time scanner, it is compatible with most antivirus or antimalware programs.