- When you start your browser, the home page has mysteriously changed. You change it back manually, but before long you find that it has changed back again.
- You get pop-up advertisements when your browser is not running or when your system is not even connected to the Internet, or you get pop-up ads that address you by name.
- Your phone bill includes expensive calls to 900 numbers that you never made-probably at an outrageous per-minute rate.
- You enter a search term in Internet Explorer's address bar and press Enter to start the search. Instead of your usual search site, an unfamiliar site handles the search.
- A new item appears in your Favorites list without your putting it there. No matter how many times you delete it, the item always reappears later.
- Your system runs noticeably slower than it did before. If you're a Windows 2000/XP user, launching the Task Manager and clicking the Processes tab reveals that an unfamiliar process is using nearly 100 percent of available CPU cycles.
- At a time when you're not doing anything online, the send or receive lights on your dial-up or broadband modem blink just as wildly as when you're downloading a file or surfing the Web. Or the network/modem icon in your system tray flashes rapidly even when you're not using the connection.
- A search toolbar or other browser toolbar appears even though you didn't request or install it. Your attempts to remove it fail, or it comes back after removal.
- And the final sign is: Everything appears to be normal. The most devious spyware doesn't leave traces you'd notice, so scan your system anyway.