NoScript - A Firefox addin that makes browsing safer.

JavaScript is a programming language that is supported by most browsers and in turn used by many web pages. With JavaScript, web page authors can do more than just display text and pictures - they can write full featured programs that actually do things in your browser.

A great example is Google Docs. Their word processing program and spreadsheet program are handled entirely within your browser, and rely heavily on JavaScript. Many websites use JavaScript for various features, and some occasionally even require it to function.

But like any programming language, JavaScript can also be used with malicious intent.

I often talk about not visiting "malicious websites", and what often makes them malicious is that they use JavaScript to fool, hack or otherwise gain access to things that you don't want them to. It's not necessarily easy, and it's not necessarily so common as to be particularly scary, but it does exist, and is another way that hackers get into things they shouldn't.

The browser pretty much lets you turn JavaScript on or off completely. That's not a practical option since so many sites - sites we trust and use every day - actually require JavaScript to operate. So we pretty much need to turn JavaScript on ... but then all sites, good or bad, can use it.

NoScript addresses this very simply. To quote their site:

... this free, open source add-on allows JavaScript, Java and Flash and other plugins to be executed only by trusted web sites of your choice (e.g. your online bank) ..."

After installing NoScript, scripting is disabled on all sites you visit. Each time you then encounter a site that you trust that requires JavaScript you tell NoScript "this site is OK". NoScript enables JavaScript for that site and remembers - you never have to tell it that site's OK again.

When you encounter a site that is not on your trusted list, NoScript's icon in the lower right of your browser window will change to indicate that scripts have been blocked, and a "Scripts Currently Forbidden" line is added:

You can then click on the NoScript icon (1) or the Options button (2) and NoScript will list the sources attempting to run JavaScript on the current web page. In this example, you would click on "Allow ask-leo.com" (3) to allow JavaScript that originates from ask-leo.com to be run.

You'll note that JavaScript often originates from sites other than the page you're looking at. In the example above. you can see that even though you are visiting ask-leo.com, JavaScript is also coming from kontera.com (4) and aweber.com. It's not at all uncommon, but worth paying attention to. In this example, Kontera.com is an advertising provider, and aweber.com is my email newsletter provider. Enabling those individually will turn on additional functionality when you view the page. Third party scripts are, most frequently, advertising, but they can also be core functionality that's required for the site to operate properly.

Once you've clicked on "Allow ask-leo.com", or any of the other domains that can be allowed, scripts originating from those domains will be allowed and run from then on.

Over time, after you build up your list of allowed sites, you'll rarely even think about NoScript unless or until you visit a site that is new, or has unexpectedly added scripting. This is where NoScript's real value comes into play: scripts from new sources will not run. Any attempts to perform malicious actions via scripting will not be able to take place until you've had a chance to determine if the site is trustworthy or not.

With malicious attacks always seemingly on the rise, blocking scripting by default and allowing on an as-needed basis make a lot of sense.

NoScript - another tool for your security arsenal.

I recommend it.