Posted by Tavis Ormandy, Security Team Panayiotis' and Niels' post on malware, I'd like to discuss a somewhat related topic, virtualisation. Virtual machines are often used by security researchers to sandbox malware samples for analysis, or to protect a machine from a potentially hazardous activity. The theory is that any security threat or malicious behaviour will be restricted to the virtual environment which can be discarded and then restored to pristine condition after use.paper at CanSecWest on a number of ways that an attacker could break out of a virtual machine.bitblt routines , which are used for moving rectangular blocks of data around the display. If exploited, by specifying pathological parameters for the operation, this could lead to an attacker compromising the virtual machine process. While you would typically require root (or equivalent) privileges in the guest to interact with a device at the low level required, device drivers will often offload the parameter checking required onto the hardware, so in theory an unprivileged attacker could be able to access flaws like this by simply interacting with the regular API or system call interface provided by the guest operating system. Reduce the attack surface By disabling emulated devices, features and services you don't need you reduce the amount of code exposed to an attacker, thus reducing the number of possible bugs that can be exploited. You should also aim to protect the integrity of the guest operating system, making it harder for an attacker to get lower level access to emulated hardware. By keeping software in the guest up to date, and hardening it by locking down the operating system and minimising what is run with root or admin privileges, you can reduce the risk of privilege escalation attacks. If an attacker cannot get low level access to the emulated hardware, it will be more difficult to exploit the bugs in them. Remember that some legacy operating systems make no attempt to restrict access to I/O ports and similar interfaces, these should be used with caution in a security sensitive context. Treat virtual machines as services that can be compromised Most administrators will take steps to limit the impact of a compromise of a network facing daemon, such as using chroot() or running the daemon as a low privileged user. These same tactics can be applied to your virtual machine. As always, try to minimise what has to run as root or administrator. Keep software up to date Keep your virtual machine software up to date, and look out for any security advisories from your vendor so that you can apply any patches promptly.
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6 commentaires :
GreenBorder / Virtualization -
Does it all go together with this article
Cant really agree more there. The simple version of this article could go as follows :
"On virtualisation : There is no silver bullet, try again"
Doublt this will stop vendors from trying to sell it as such silver bullet. Ah, we will see :)
icarus. I dont think the vendors are selling virtual machines as a silver bullet to solve the malware problem. Security research is simply another application of VM. Many IT admins use VM technology to consolidate their IT services onto one machine, instead of having a different physical machine for each service... VM is also VERY useful for software testing too....
//Steve Jackson
Malware Researcher
btw. Nice to see Google having a security related blog!!
//Steve
Security researchers use VMs because they have handy snapshot and revert features.
Some OSes have snapshot and revert features, but they are inconvenient to use.
I'd agree that VMs are just another container like processes, chroot jails, etc. which offer some security properties, but are not a magic bullet.
-chris wee
Unfortunately, virtualization has a lot of security-related problems. It require constant revert to original state. Sandbox HIPS without virtualization (DefenseWall HIPS, GeSWall) gives much more security to their users compare to sandbox HIPS with virtualization (ex-Greenborder, SandboxIE,...).
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