Firefox highlights such problems through an error console (previously called JavaScript console), as illustrated in Figure 1.9. Another problem is that web sites that use JavaScript may not be coded correctly, causing difficulties for the browser. Significantly, this facility works much like the proposed two-level model might behave, in that it involves management monitoring superimposed on functional behaviour. Currently, this is about 10% of those assessed. The report for dubious sites can be examined in detail before entry but for most users all sites graded yellow or red would probably be avoided. A green, yellow or red tag is attached if the site has been rated by SiteAdvisor otherwise a question mark is used. Following a web search, using an established engine such as Google, Yahoo or Ask Jeeves, the presented page of links is analyzed and tags added to each link. This includes misusing supplied e-mail addresses or including malware in downloads. red, warning, if tests and manual analysis reveal serious issues to consider before accessing the site.yellow, caution, if tests reveal some minor security or nuisance issues or the site has had past security issues or.green, safe, with no significant problems found.SiteAdvisor uses web crawlers to examine sites on the Internet and rate them as: One good example is McAfee SiteAdvisor which was developed in 2005 by a small start-up at MIT, before being taken over in 2006 by McAfee. Likewise, the same mechanism may extend the service management part. Some plug-ins enhance the functionality of a browser and so conceptu- ally extend the “service supplier” part of the application. Currently, management of these facilities is mixed with other functionality in browsers, so location in a two-level framework would again be beneficial. Because of their risk, however, they may be blocked, possibly by default, with the user giving explicit approval if any are needed (Figure 1.8). All of these facilities have perfectly legitimate uses and indeed may be essential for some sites. The embedding of JavaScript in the underlying HTML code. Examples include Macromedia Flash Player and Java. Plug-ins, which add new capabilities to a browser, such as the ability to play audio or video clips. Cookies, files created by a web site to store information on a user’s computer about use of that site. Pop-up windows, that appear on entry to a site. Sources of vulnerability include the use of: 1. Browsers have a basic vulnerability because they may connect to sites that are “malicious”. In the two-level model, such error handling would be a management level responsibility. Some of these may indicate a problem with Firefox so this mechanism is also useful for error reporting in general. Firefox caters for this possibility by allowing users to report “broken web sites”, as indicated in Figure 1.7. This can occur if the site is developed using features supported only by a particular type of browser, or even a particular version of a browser. One basic problem with a browser is that it may not present pages as intended by the web site designer. Instead, therefore, some form of soft query to management level software is preferable, allowing for a controlled termination of the transaction or perhaps an explanation of the delay. One difficulty, however, is that the user may be involved in an extended transaction at that point, such as paying for a service or product by credit card, so breaking the connection may leave the transaction in an uncertain state. If a browser “hangs” in interacting with a web site it can be cleared with the stop button if it fails to “time out”. For browsers, there is less data involved so saving and restoring a state is more straightforward. Firefox, for example, saves information about the web sites it has open at the time of closure and the session restored to that state when it is re-opened ( Figure 1.6). In particular, the state of a browser can be saved periodically so that recovery is possible in the event of failure. With increasing web site sophistication and complexity, browsers now also share similar problems to other applications and so can benefit from the two- level approach in the ways outlined for Microsoft Word in the preceding sub- section. That is, like Microsoft Word, browsers mix functional and management activities in a single piece of software, rather than separate them out, as proposed in the two-level self-management model. web browser, such as Internet Explorer, Firefox or Opera, is similar in structure to most other applications.
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