Q: I read your column about preventing "drive-by download" attacks that try to put malware on phones with the Android operating system (see tinyurl.com/y8e37w4b). How can iPhone owners protect themselves?

Joe Schaefer, Colorado Springs, Colo.

A: IPhones aren't as susceptible to drive-by malware attacks as Android phones are. That's because iPhone users can download only apps that have been approved as safe by Apple. Here's how it works:

Android phones have two download settings. One setting allows the user to download apps only from the Google Play store, where apps are supposed to be screened for malware. The other setting allows apps to be installed from any website, whether it checks for malware or not.

That second setting also opens up Android phones to drive-by malware attacks, in which disreputable websites prompt users to accept app downloads that they didn't request — downloads which really contain malware.

IPhones are set to allow downloads only from Apple's App Store, and consumers can't change that setting as part of the phone's normal operations. Because users can't download apps from anywhere else, drive-by malware attacks on the iPhone aren't possible.

However, that doesn't mean that iPhones are immune to malware. New vulnerabilities in the iPhone's iOS operating system are discovered periodically, forcing Apple to issue software patches to protect the phones (see tinyurl.com/lael6fo). In addition, some iPhone owners have courted trouble by using special non-Apple software to "jailbreak" their phones. Jailbreaking allows an iPhone to download and install apps from non-Apple websites. But it also disables part of the iPhone's security software, leaving the phone vulnerable to many types of malware attacks.

Q: I've always shut down my Dell Windows 7 PC by using the "shut down" command, or, if I have a problem, by forcing the PC to shut down by pushing and holding the power button. But now my PC often can't find my Wi-Fi router (only 4 feet away) unless I restart the PC several times. I tried restarting the router and modem, but it made no difference. What can I do?

Luke Parmelee, Columbus, Ohio

A: Windows needs to be shut down in an orderly way, and your forced shutdowns have probably damaged the operating system. If you have a Windows installation disk or system repair disk, try fixing Windows 7 (see "How to run a repair" at tinyurl.com/y7f5e2kg).

If you don't have those disks, buy a new copy of Windows 7 ($115 to $140 at tinyurl.com/y8h9j5f6 and tinyurl.com/y8t3vas2). Before installing it, back up your data to a flash drive or external hard drive, because the process erases everything on the hard disk. You will need to reinstall software you added to the PC, then copy your data back to the hard disk.

For simplicity, and because you have an undependable Wi-Fi connection, buy Windows 7 on a DVD disk, not as a download. Make sure you buy the correct (32-bit or 64-bit) version of Windows 7. To find out which your PC uses, go to Control Panel and click System.

E-mail tech questions to steve.j.alexander@gmail.com. Include name, city and telephone number.