Few people are aware of Windows XP’s cloaked administrator account (called, appropriately enough, “Administrator”). This account is invisible unless either your system has no other accounts or you are booting in Safe Mode. To remove Administrator’s camouflage and add it to XP’s Welcome screen, navigate to and then select HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList in the Registry Editor, and double-click the Administrator icon in the right pane. (If you don’t see this icon, right-click in the pane, choose New, DWORD Value, name it Administrator, and press <Enter>.) Type 1 in the ‘Value data’ box, and press <Enter>. From now on, when you open the User Accounts window via the Control Panel (choose Start, Run, type Control userpasswords, and press <Enter>), you’ll see the Administrator account. You can easily change its picture or give it a password. In addition, the next time you see the Welcome screen, your Administrator account will be visible, along with all of the computer’s other user accounts.


Find Every File

When you search for a file in Windows (choose Start, Search, For Files or Folders, or press in any Explorer or folder window to open the search pane), Windows searches only for file types it recognizes. Files that aren’t listed in the ‘Registered file types’ list are ignored (to view this list, open Explorer, choose Tools, Folder Options, and click the File Types tab). So while ‘Read_Me.xyz’ may be a perfectly good file name to you, Windows pays it no mind because of the unrecognized ‘.xyz’ file extension. Fortunately, a simple edit of the Registry will make Windows search for every file, regardless of its extension. Open the Registry Editor as described above, and then navigate to and select HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ContentIndex. Double-click the FilterFilesWithUnknownExtensions icon in the right pane, change the 0 in the ‘Value data’ box to 1, and press <enter>.

If you just switched to a wide-screen monitor, your desktop wallpaper image may no longer look right, or maybe you just want to make a small adjustment to it. For more-granular control of your wallpaper’s placement, highlight the HKEY_CURRENT_USER\Control Panel\desktop key in the Registry Editor, and double-click the WallpaperOriginX icon in the right pane. (If you don’t see this icon, right-click in this pane, choose New, String Value, type WallpaperOriginX to name the value, and press <Enter>.) Type a number (in pixels) for the starting horizontal position of your wallpaper’s left edge, and press <Enter>. Now double-click the WallpaperOriginY icon (create it if necessary as explained above) and enter a number for the starting vertical position of the image’s top edge. If your wallpaper image is larger than the screen, type a negative number (for example, -200) to push the picture’s top or left edge off the screen.

To test the effect, first minimize the Registry Editor (and any other open window), right-click the desktop, choose Properties, and click OK or Apply to refresh the wallpaper placement. Repeat these steps as needed until the wallpaper is positioned correctly. The settings work whether you’ve set your wallpaper to be centered, tiled, or stretched.

We’ve all seen it: You try to exit a program (or Windows itself), and you end up waiting for one or more apps to shut off. After a while–a long while in some cases–Windows gives up waiting too, and displays the End Program dialog box so you can force the programs to close.

Patience is a virtue, but if Windows is taking too long to shut down recalcitrant programs, you can tell it to show the End Program option sooner. In fact, you can make Windows close the hung application without bothering you with a dialog box at all. Keep in mind, however, that if you choose the promptless option, you may damage your system settings by squashing a hung Windows process too quickly. (There’s a middle road: You can retain the prompt and use a shorter timeout interval, since the dialog box always gives you the option of waiting longer.)

To make Windows automatically end hung processes, launch the Registry Editor as described previously, and navigate to and select HKEY_CURRENT_USER\Control Panel\Desktop. Double-click the AutoEndTasks icon in the right pane, change ‘Value data’ to 1, and press <Enter>. (Change it back to 0 if you later decide to revert to manual shutdown control.)

Next, double-click the HungAppTimeout icon in the same pane, and edit the ‘Value data’ field to reflect the time (in milliseconds) you are willing to wait for an unresponsive application.  The default setting is ‘5000’, or 5 seconds. To reset the wait time for a program that is slow to shut down when Windows exits, double-click the WaitToKillAppTimeout icon in the same Registry pane, change the default of ‘20000’ (milliseconds, or 20 seconds) to the maximum wait time of your choice, and press <Enter>.

Applications aren’t the only things that may keep you waiting for Windows to shut down. The operating system’s many running processes (also known as “services”) have their own timetable for shutting down. To designate a maximum wait time before Windows ends (or prompts you to end) services at shutdown, open the Registry Editor, and navigate to and select HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control. Double-click the WaitToKillServiceTimeout icon in the right pane. Adjust its ‘Value data’ (also 20000 milliseconds, or 20 seconds, by default) to the wait time of your choice, and press <Enter>. Note: Your new value may not stick, since some services automatically increase this number to build in more time to clean up their act.

How Google Works

Google runs on a distributed network of thousands of low-cost computers and can therefore carry out fast parallel processing. Parallel processing is a method of computation in which many calculations can be performed simultaneously, significantly speeding up data processing. Google has three distinct parts:

Googlebot, a web crawler that finds and fetches web pages.

The indexer that sorts every word on every page and stores the resulting index of words in a huge database.

The query processor, which compares your search query to the index and recommends the documents that it considers most relevant.

Let’s take a closer look at each part.

1.  Googlebot, Google’s Web Crawler

Googlebot is Google’s web crawling robot, which finds and retrieves pages on the web and hands them off to the Google indexer. It’s easy to imagine Googlebot as a little spider scurrying across the strands of cyberspace, but in reality Googlebot doesn’t traverse the web at all. It functions much like your web browser, by sending a request to a web server for a web page, downloading the entire page, then handing it off to Google’s indexer.

Googlebot consists of many computers requesting and fetching pages much more quickly than you can with your web browser. In fact, Googlebot can request thousands of different pages simultaneously. To avoid overwhelming web servers, or crowding out requests from human users, Googlebot deliberately makes requests of each individual web server more slowly than it’s capable of doing.

Googlebot finds pages in two ways: through an add URL form, http://www.google.com/addurl.html, and through finding links by crawling the web.

Unfortunately, spammers figured out how to create automated bots that bombarded the add URL form with millions of URLs pointing to commercial propaganda. Google rejects those URLs submitted through its Add URL form that it suspects are trying to deceive users by employing tactics such as including hidden text or links on a page, stuffing a page with irrelevant words, cloaking (aka bait and switch), using sneaky redirects, creating doorways, domains, or sub-domains with substantially similar content, sending automated queries to Google, and linking to bad neighbors. So now the Add URL form also has a test: it displays some squiggly letters designed to fool automated “letter-guessers”; it asks you to enter the letters you see — something like an eye-chart test to stop spambots.

When Googlebot fetches a page, it culls all the links appearing on the page and adds them to a queue for subsequent crawling. Googlebot tends to encounter little spam because most web authors link only to what they believe are high-quality pages. By harvesting links from every page it encounters, Googlebot can quickly build a list of links that can cover broad reaches of the web. This technique, known as deep crawling, also allows Googlebot to probe deep within individual sites. Because of their massive scale, deep crawls can reach almost every page in the web. Because the web is vast, this can take some time, so some pages may be crawled only once a month.

Although its function is simple, Googlebot must be programmed to handle several challenges. First, since Googlebot sends out simultaneous requests for thousands of pages, the queue of “visit soon” URLs must be constantly examined and compared with URLs already in Google’s index. Duplicates in the queue must be eliminated to prevent Googlebot from fetching the same page again. Googlebot must determine how often to revisit a page. On the one hand, it’s a waste of resources to re-index an unchanged page. On the other hand, Google wants to re-index changed pages to deliver up-to-date results.

To keep the index current, Google continuously recrawls popular frequently changing web pages at a rate roughly proportional to how often the pages change. Such crawls keep an index current and are known as fresh crawls. Newspaper pages are downloaded daily, pages with stock quotes are downloaded much more frequently. Of course, fresh crawls return fewer pages than the deep crawl. The combination of the two types of crawls allows Google to both make efficient use of its resources and keep its index reasonably current.

2.  Google’s Indexer

Googlebot gives the indexer the full text of the pages it finds. These pages are stored in Google’s index database. This index is sorted alphabetically by search term, with each index entry storing a list of documents in which the term appears and the location within the text where it occurs. This data structure allows rapid access to documents that contain user query terms.

To improve search performance, Google ignores (doesn’t index) common words called stop words (such as the, is, on, or, of, how, why, as well as certain single digits and single letters). Stop words are so common that they do little to narrow a search, and therefore they can safely be discarded. The indexer also ignores some punctuation and multiple spaces, as well as converting all letters to lowercase, to improve Google’s performance.

3.  Google’s Query Processor

The query processor has several parts, including the user interface (search box), the “engine” that evaluates queries and matches them to relevant documents, and the results formatter.

PageRank is Google’s system for ranking web pages. A page with a higher PageRank is deemed more important and is more likely to be listed above a page with a lower PageRank.

Google considers over a hundred factors in computing a PageRank and determining which documents are most relevant to a query, including the popularity of the page, the position and size of the search terms within the page, and the proximity of the search terms to one another on the page. A patent application discusses other factors that Google considers when ranking a page. Visit SEOmoz.org’s report for an interpretation of the concepts and the practical applications contained in Google’s patent application.

Google also applies machine-learning techniques to improve its performance automatically by learning relationships and associations within the stored data. For example, the spelling-correcting system uses such techniques to figure out likely alternative spellings. Google closely guards the formulas it uses to calculate relevance; they’re tweaked to improve quality and performance, and to outwit the latest devious techniques used by spammers.

Indexing the full text of the web allows Google to go beyond simply matching single search terms. Google gives more priority to pages that have search terms near each other and in the same order as the query. Google can also match multi-word phrases and sentences. Since Google indexes HTML code in addition to the text on the page, users can restrict searches on the basis of where query words appear, e.g., in the title, in the URL, in the body, and in links to the page, options offered by Google’s Advanced Search Form and Using Search Operators (Advanced Operators).

For the first few decades of their existence, computer networks were primarily used by university researchers for sending e-mail and by corporate employees for sharing printers. Under these conditions, security did nit get a lot of attention. But now, as millions of ordinary citizens are using networks for banking, shopping and filling their tax returns, network security is looming on the horizon as a potentially massive problem. In this section, we will discuss network security from several angles, point out numerous pitfalls and discuss many algorithms and protocols for making networks more secure.

This document was written with the basic computer user and information systems manager in mind, explaining the concepts needed to read through the hype in the marketplace and understand risks and how to deal with them.

Some history of networking is included, as well as an introduction to firewalls and internetworking. We go on to consider risk management, network threats, firewalls, and more special-purpose secure networking devices.