So it's Friday afternoon, the weekend is just around the corner, and you're up to no good. Rather than waste your time turning monitors upside down around the office, why not update your tech arsenal? If you have a computer or cell phone on hand, you're more than ready to beef up your weapons and spy kit with these 12 sly tricks. We'll teach you why and how (and with what) to do them, and tell you how well you can expect them to work. And you will forget where you heard this information...

Turn Wi-Fi Thieves' Worlds Upside Down
The problem: You took the time and expense to set up a wireless Internet connection at your place. But you're pretty sure that the cheap bastard next door is stealing it--that is, connecting to the Internet on your dime. Sure, you could take the easy step of password-protecting your network, but what fun is settling for a little common-sense measure like that?

The trick: With the help of a lovely little service called Upside-Down-Ternet, you can turn that Wi-Fi thief's free Internet scheme upside down--literally. With a little clever scripting, every image the thief views via your connection is flipped upside down on his monitor and mirrored, making Web browsing difficult to say the least. You can also redirect every Web request the thief makes to a particular site--the author of the hack suggests Kittenwar. Pretty good, but I would go with an old standby.

The effect: The trick takes a little work to set up right, but if you can pull it off, it works perfectly. And doing right by one's neighbor just makes you feel good inside.

Never Be 'Away' With Your AIM Bot
The problem: Some employers use IM clients to track their workers and ensure they're keeping their noses to the grindstone--but, hey, you don't like Big Brother staring over your shoulder.

The trick: Create your own AIM bot with the Web site RunABot. An AIM bot is an automated chat robot that resembles any other AIM user, and--if you set it up well--it responds to messages like a real person. Once you register with RunABot, the site walks you through setting up your bare-bones bot; then it's up to you to make your bot believable.

The effect: In the time it takes to customize your bot to fool your boss in all situations, you could probably finish several work projects and earn a few promotions. With just a few minutes of setup time, however, the "hardworker" bot I put together can convincingly participate in simple workplace conversations.

Make a Laptop Thief Regret It
The problem: Every time you leave your table at the bookstore for another cup of coffee, you've got to choose what to do with your laptop. You'll only be gone for a few seconds, so lugging it with you is a pain. Still, the guy with a double espresso has been eyeing your gear since you sat down, and he looks like he could have sticky fingers.

The trick: Install an antitheft program on your laptop that monitors unusual behavior when you're away, setting off an alarm whenever it detects a possible theft. The freeware Windows application Laptop Alarm sounds an alarm whenever your laptop's power cable is unplugged, the mouse is moved, or the laptop is shut down. Mac users should check out iAlertU , a freeware app that uses your MacBook's built-in accelerometer to set off the alarm and snag a Webcam picture whenever someone so much as moves your laptop. You can smoothly disable the alarm with your Apple remote like a proper car alarm.

The effect: Under the right circumstances, these applications can be enough to deter a thief from running off with your laptop. Neither application is foolproof, however: Don't consider these apps as anything more than deterrents.

Spoof Your Caller ID
The problem: Before caller ID became standard on every phone, making an anonymous call meant little more than dialing the number. Today it's easy to screen calls and send unknown numbers to voicemail. If you're looking to make an old-fashioned prank call (heavy breathing optional) or simply surprise the person you're calling, the ubiquity of caller ID has ruined the fun.

The trick: Several caller ID spoofing services are available online that not only hide your number from the recipient's caller ID, they also make the call appear to be coming from another phone number altogether. Even better, you decide what number you want to show up when you call. I tested this trick at SpoofCard, one of many such services. Just give SpoofCard your number, the number you want to call, and the number you want to show up in the caller ID; SpoofCard takes care of rest.

The effect: SpoofCard was very easy to use, and it did exactly what it advertised. In my test, that meant spoofing with Tommy Tu-Tone's 867-5309 without a hitch. SpoofCard offers free trial calls, which is probably enough for most users.

Did They Read Your E-Mail? When?
The problem: You send out an important e-mail message reminding your coworker to bring copies of your PowerPoint presentation to the big meeting. You get there, and he doesn't have them. His excuse: He never got your e-mail. Possible, but questionable; anyway, you want to know for sure.

The trick: Send messages you want to monitor through DidTheyReadIt. The Web site embeds a tiny image in each e-mail it sends. When the e-mail is opened, the recipient's e-mail client, in many cases, will automatically send a request for the embedded image; when that request is made, DidTheyRead then knows that the e-mail was indeed opened, when it was opened, and for how long it was open.

The effect: If you really need to be sure that someone received a particular message, DidTheyReadIt works as advertised. The only catch: If the recipient's e-mail client doesn't automatically download embedded images, DidTheyReadIt's tracking mechanism may not work.

Create a Web-Streaming Spycam
The problem: You want to keep a closer eye on your kids when you're away without having to buy a nanny cam.

The trick: The free application WebcamXP streams video from your Webcam over the Internet so you can keep an eye on your home from anywhere. If you have a Webcam with a tracking motor, WebcamXP can even control the pan and tilt of the camera over the Internet, giving you full control over what you're seeing.

The effect: The application works very well, though the free version supports just one video source. Upgrading to one of the shareware versions gives you motion detection, and the ability to hook up and view feeds from multiple Webcams.

Crack a Windows Password

Crack a Windows Password
The problem: You lost your Windows password (or you want to discover someone else's). Now you have no way to fully access your account without getting it back.

The trick: Download Ophcrack Live CD and burn it to a disc; then restart your computer and boot from the CD. Point Ophcrack at the hard drive where Windows is installed, and it'll start cracking your Windows password.

The effect: The shorter and simpler the Windows password, the more quickly and easily Ophcrack will break it. But Ophcrack can only crack alphanumeric passwords. If the password contains other characters or symbols (like "@"), Ophcrack won't do the job.

Read Books on the D.L. at Work
The problem: Whether or not you've got any work to do, most employers frown on cracking a book at your desk.

The trick: Web site Read at Work is a full-screen Flash application that mimics a Windows desktop and serves up public-domain works in a format that resembles PowerPoint presentations. Classics by Twain, Fitzgerald, Dickinson, and Tolstoy are all yours to read on company time. (Well, if it's Tolstoy, you might rather just work).

The effectiveness: To the casual onlooker, Read at Work convincingly looks like a standard Windows XP window. Whether or not your boss will believe that the Oscar Wilde you're reading is actually a PowerPoint presentation depends on your boss. And it helps if reading PowerPoint presentations is actually part of your job.

Say It With Self-Destructing E-Mail
The problem: E-mail is forever. If you fire off an angry or ill-thought-out message, the recipient could hold onto it--and hold it against you--indefinitely.

The trick: Send a self-destructing e-mail message by going to the Web site DestructingMessage. Just specify how much time you want to give the recipient before the message implodes (15 seconds to 5 minutes), write your message, and send it.

The effect: DestructingMessage can send the e-mail anonymously, or you can send a link to the message yourself. Either way, the recipient has a limited time to read it before it's gone for good. If the recipient is quick on her feet, though, she could grab a screen shot before it's gone forever.

Go Straight to Voicemail
The problem: Everybody's been there. You'd rather leave a voicemail than deal with a drawn-out phone conversation. Or you're a coward with bad news to deliver.

The trick: SlyDial connects you directly with your contacts' voicemail--whether they've got their phone turned on or not. Just dial 267-SLYDIAL, enter the number you want to leave a voicemail with, and then, when prompted, just leave your message.

The effect: SlyDial works exactly as advertised. Use SlyDial gratis as much as you want, but if you tire of the in-call advertising, premium plans get you to voicemail faster and ad-free. SlyDial voicemails, however, do not self-destruct--I guess they haven't thought of that yet.

Spoof Your E-Mail Address
The problem: You want to send e-mail from a bogus account.

The trick: Forge an e-mail address with your desktop e-mail client. In Thunderbird, all you need is a working SMTP server and a fake account. As long as the SMTP server can send e-mail without requiring authentification, you can use your fake e-mail address as much as you want.

The effect: To most people, your spoofed e-mail will appear indistinguishable from a real one. The catch: You won't get any replies, and a look at the message's headers can reveal to the recipient that you're using an unusual SMTP server for that e-mail address.

Browse the Net Without Leaving a Trace
The problem: Web sites you visit are tracked by your Web browser in several ways that aren't immediately obvious--such as browser history, cookies, or cached files. Whether you're doing some online shopping on a shared computer or visiting Web sites that are, let's say, embarrassing, it's hard to make sure that a browsing session doesn't leave a trace.

The trick: Go off the record when you want browsing privacy with the Stealther Firefox extension. Enabled, Stealther makes sure that your browsing history, downloads, disk cache, saved form information, and cookies aren't saved to your browser.

The effect: Stealther works in every respect. Whenever you want to go off the record with your browsing, just go to Tools, Stealther. When you're ready to go back on the record (after all, browser history and cookies can be very useful), just turn off Stealther. Muahahahahaha!!!

This story originally appeared on PCWorld