PERSONAL TECH

Avoiding Botnets With a Mac

Q&A 
By  
Avoiding 
The Mac Botnet
Q. Is this just a Windows problem, or are there botnets made up of Macs all infested with bot programs? If there is such a thing, how can I protect my Mac from infection?
A. Windows-based PCs are the main targets of the malicious software that loops infected computers into a remote-controlled network called a botnet, but Macs are not immune. Last fall, the iWorm botnet snared more than 18,500 Macs and allowed hackers to remotely download files, relay Internet traffic and perform other tasks.
Apple built several security features into recent versions of OS X, including a malware-detection tool that checks a list of known malicious software and warns you about it; the company quickly updated the list last fall when iWorm was discovered. Apple also issues regular security updates for OS X, so be sure your Mac has the latest updates installed. If you do not have updates set to install automatically, you can manually check and install them as explained at support.apple.com/en-us/HT201541.
Intego, one of the companies that offers antivirus software for Mac OS X, posted an extensive analysis of the iWorm Botnet on its security blog. All the company’s posts on the topic (including how to check for infection) can be found by searching for “iWorm” at www.intego.com/mac-security-blog. Intego, though, is just one of several Mac antivirus companies, and iWorm was just one of the Mac-based botnets.
Viruses and malware aimed at OS X are becoming more common as Macs continue to gain popularity. If you are worried about safety beyond what OS X provides, you can find several third-party security programs in the Mac App Store (under the Mac’s Apple menu) or online from major antivirus companies.
Erasing 
A Memory Card
Q. I have successfully downloaded photos from my camera to my computer but cannot find a command to delete them from the memory card. How do I remove the pictures?
A. When you import the photos to the computer, the program that copies the images may offer to erase them from the camera’s memory card for you once they are safely on your hard drive; you may also see a “Delete after import” box to check. (Image Capture or iPhoto on the Mac, or the AutoPlay box that pops on in most versions of Windows can all do this.) Choosing this option removes the photos from the camera’s memory card, but make sure everything copied over first.
The memory card is basically a storage device like a USB drive. After you import the pictures to a folder or program, you can also delete them from the card by dragging the files to the trash, as you would with a USB drive.
Your camera’s manual should have instructions for deleting photos one at a time or all at once. Most cameras also have a menu command to format the memory card, which, in addition to erasing everything on the card, freshly creates the card’s file system and helps its overall performance.
TIP OF THE WEEK Getting directions from your current location to a specific address with the Google Maps mobile app can help you get around in an unfamiliar area. Nevertheless, if you are unsure about which way to go first, you can have the app point you in the right direction.
Once you have entered your destination’s address (or marked it with a pin on the map) and tapped the button for directions, tap the compass icon on the right side of the screen. The map then orients itself on the screen so you see it from your current point of view and you can start off going the correct direction. J.D. BIERSDORFER
Personal Tech invites questions about computer-based technology to QandA@nytimes.com. This column will answer questions of general interest, but letters cannot be answered individually. 
A version of this article appears in print on January 29, 2015, on page B8 of the New York edition with the headline: Avoiding Botnets With a Mac. Order Reprints|  Today's Paper|Subscribe