Sandbox (computer security)
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In computer security, a sandbox is a security mechanism for separating running programs. It is often used to execute untested code, or untrusted programs from unverified third-parties, suppliers, untrusted users and untrusted websites.
The sandbox typically provides a tightly controlled set of resources for guest programs to run in, such as scratch space on disk and memory. Network access, the ability to inspect the host system or read from input devices are usually disallowed or heavily restricted. In this sense, sandboxes are a specific example of virtualization.
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Examples of sandboxes include:
- Applets are self-contained programs that run in a virtual machine or scripting language interpreter that does the sandboxing. In application streaming schemes, the applet is downloaded onto a remote client and may begin executing before it arrives in its entirety. Applets are common in web browsers, which use the mechanism to safely execute untrusted code embedded in web pages. Three common applet implementations—Adobe Flash, Java applets and Silverlight—provide (at minimum) a rectangular window with which to interact with the user and some persistent storage (at the user's permission).
- A jail is a set of resource limits imposed on programs by the operating system kernel. It can include I/O bandwidth caps, disk quotas, network-access restrictions and a restricted filesystem namespace .. Jails are most commonly used in virtual hosting.
- Rule-based Execution gives users full control over what processes are started, spawned (by other applications), or allowed to inject code into other apps and have access to the net- by having the system assign access levels for users or programs according to a set of determined rules. It also can control file/registry security (what programs can read and write to the file system/registry). In such an environment, viruses and trojans have fewer opportunities of infecting a computer. The SELinux and Apparmor security frameworks are two such implementations for Linux.
- Virtual machines emulate a complete host computer, on which a conventional operating system may boot and run as on actual hardware. The guest operating system runs sandboxed in the sense that it does not function natively on the host and can only access host resources through the emulator.
- Sandboxing on native hosts: Security researchers rely heavily on sandboxing technologies to analyse malware behaviour. By creating an environment that mimics or replicates the targeted desktops, researchers can evaluate how malware infects and compromises a target host.
- Capability systems can be thought of as a fine-grained sandboxing mechanism, in which programs are given opaque tokens when spawned and have the ability to do specific things based on what tokens they hold. Capability based implementations can work at various levels, from kernel to user-space. An example of capability-based user-level sandboxing involves HTML rendering in a Web browser.
- Online judge systems to test programs in programming contests.
- New-generation pastebins allowing users to execute pasted code snippets.
- Secure Computing Mode (seccomp) is a sandbox built in the Linux kernel. When activated seccomp only allows the write(), read(), exit() and sigreturn() system calls.
- HTML5 has a "sandbox" attribute for use with iframes 
- Applications for Apple's mobile operating system iOS are sandboxed. They are only able to access files inside their own respective storage areas, and cannot change system settings.
- Ian Goldberg, David Wagner, Randi Thomas, and Eric Brewer (1996). "A Secure Environment for Untrusted Helper Applications (Confining the Wily Hacker)". Proceedings of the Sixth USENIX UNIX Security Symposium. Retrieved 25 October 2011.
- "What Applets Can and Cannot Do". The Java Tutorials. 1995, 2013. Retrieved 28 April 2013.
- "Sandboxing Applications". 2001. Retrieved 7 May 2013.
- "Computer System Security and Access Controls". 1991. Retrieved 17 May 2013.
- http://blogs.msdn.com/b/ie/archive/2011/07/14/defense-in-depth-locking-down-mash-ups-with-html5-sandbox.aspx, IEBlog