This is a very interesting question. There is, indeed, an issue with establishing the security, veracity and stability
of Firefox and other Mozilla product extensions, now known as add-ons. For example, in July of 2006 a fake Firefox add-on was discovered to have attempted to steal passwords and perform key logging after installation. This add-on was particularly worrying because it was capable of being installed without prompting the user.
Unfortunately, there isn't a ready way to determine whether an extension is malicious. One of the few ways is doing basic research. I recommend using Google or your choice of search engine to find information about the add-on you wish to use. If the add-on is malicious, hopefully someone else has encountered it before and has identified its malicious nature. Checking the sites for the major anti-virus vendors is also recommended. They are often the first groups to identify threats and alert on them.
Probably the (comparatively) safest way to download and install add-ons is via the Mozilla Add-Ons site. Add-ons to the site should have a sponsor who tries to ensure the add-on is of a sufficient quality and appropriate nature. A review process should take place before plug-ins are added and available for download. However, the results of this review process do not appear to be documented anywhere, nor does there appear to be a standard security policy for Mozilla add-ons.
It should also be noted that, while Mozilla has a policy for the management and review of add-ons, it does not offer any liability in the event something goes wrong -- either in terms of functionality or security. The policy is also in draft.
The other obvious mitigation for potentially malicious add-ons is the use of good anti-virus and personal security tools, like personal firewalls, anti-spam and anti-spyware tools. The latter are strongly recommended. Many of these tools will alert you to malicious activity or prompt you for a response if unusual activity is detected. You then have the option of denying that activity.
In summary, the use of most Firefox (and Thunderbird and other Mozilla tools) add-ons is at your own risk. This is a great shame as they represent some excellent and useful enhancements to the Mozilla suite of products. If, like me, you are a fan of and are serious about making use of Mozilla products and the add-ons for them, then I recommend you contact Mozilla and suggest that they put in place a transparent and formalized process for the submission, review and certification of add-ons. This should be backed up by digital signatures for add-ons that have passed this review and been "certified" for use with Mozilla products. I would suggest the addition of this process would also likely increase the level of quality control for Mozilla add-ons.
Dig deeper on Linux system security best practices
Related Q&A from James Turnbull
A user wants to implement OSSEC on a Windows server because he has no server side Linux operating system.continue reading
Solaris 10 Trusted Extensions and SELinux are best suited to different system requirements and administrator skill sets. Our security expert explains...continue reading
Configuring spam filters Spamassassin and dspam together in the email server Postfix is easy with the resources listed by our security expert.continue reading
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.