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This chapter is from the book

Securing Your Email

Email is one of the primary ways bad guys get into Windows boxes, which are still the majority of desktop computers out there. Fortunately, Google has placed several smart protections into Gmail in an effort to minimize the security risks of its email.

Checking for Viruses

Google has virus checking built in to Gmail, which is a very good thing (it's not so much necessary for Linux or Mac OS X boxes, but it's really nice for the Windows users). Attachments you send and receive are scanned for malware every time you open the message containing the attachment.

If Google finds a virus in a message sent to you, it will try to clean the file so that you can still use it, but if the file can't be cleaned, it's off limits to you. Again, a good thing. If Google has a problem scanning the file, for whatever reason, it will notify you with a small alert. At that point, you can wait or go ahead and download the file at your own risk. That's not a good idea, in my opinion, unless you know you have really good antivirus protection on your PC.

If Google finds a virus in a message you're trying to send, it displays an alert to you, but it won't clean the file. That's up to you. Google does give you an option to Remove Attachment and Send, but that may not be what you want because the attachment may be vitally important to the message. Hopefully, though, a virus-laden attachment isn't vitally important to the message.

Even with the virus scanning, however, Google doesn't allow certain file types to be sent or received at all, including (but not limited to):

  • .exe
  • .dll
  • .ocx
  • .com
  • .bat

If you try, you'll see the following error message: "This is an executable file. For security reasons, Gmail does not allow you to send this type of file."

You might think that you can just zip up the attachment and sneak it past Google that way, but that won't work. Google scans the compressed file, figures out that it contains a verboten file type, and puts up a stop sign. Other compression formats, such as TAR, TGZ, Z, and GZ, don't work either. For some weird reason, though, RAR is allowed.

Industrious Gmail users have figured out a few ways to get around the restriction against sending executable files, however. I'm not saying that you should do any of these, although some are a lot safer than others, but here are a few ideas:

  • Rename the file extension from .exe to .123, or from .bat to .bat.removeme. Of course, tell your recipients in your email message that they need to change the extension.
  • Zip the file, then zip the Zip file, and password-protect the container ZIP file.
  • Use compression software that creates RAR files. Google is your friend.
  • Perhaps the easiest solution is using something like YouSendIt (www.yousendit.com), Box.net (www.box.net), or any of the others listed at http://en.wikipedia.org/wiki/One-click_hosting. If you don't know about them, check them out—you'll find them quite useful, and they complement Gmail well.

Stopping Image Spam

Gmail does an excellent job detecting spam, but a few can get through. One of the most annoying types of spam is image spam, in which a spammer has nothing but a picture in the body of the email. By using an image, spammers hope that it will be harder for Gmail's antispam tools to detect their come-ons. Here's a good way to make sure none of that junk gets into your Inbox.

Create a filter with these criteria:

  • Has the Words: type "multipart/related.gif"
  • Check the box next to Has Attachment

For the filter's actions, use these:

  • Skip the Inbox (Archive It)
  • Apply the Label: Image Spam

You may get false positives, which is why you're applying a label to the message. Check the messages in that label every once in a while to make sure there's nothing in there that you want and also to delete junk in there permanently.

Another way to help make spam more obvious when you look at the list of conversations in the Image Spam label is to use the Personal Level Indicators. To turn them on, in Gmail, go to Settings, General, Personal Level Indicators, and select Show Indicators. After you do so, a single right-pointing angle quotation mark (>) appears in front of messages in which your email address is in the To or CC field, and a right-pointing double angle quotation mark (») appears in front of messages sent only to you.

If you see a message that has a > or » in front of it, it's less likely that it's spam and more likely that's it's legit, but if you see a message without either symbol in front of it, it's more likely that it's spam and less likely that it's legit.

Finding Out Who's Accessing Your Gmail Account

If you think someone may have hacked into your Gmail account, you now have a way to tell, thanks to a feature recently added by Google. Scroll to the bottom of the main page, and you'll see text that says something like this:

This account is open in 1 other location at this IP ( Last
account activity: 1 minute ago.

This lets you know if another computer is accessing your Gmail account. In my case, it's perfectly okay that my account is open in two locations at my IP address because I'm looking at Gmail in two browsers (I'm writing a book on the subject, after all!).

If you want to know more, click the Details link. On that page, you'll see all recent activity, including the type of access (browser, POP, IMAP, or SMTP), the IP address of the accessing device, and the time of access. If one of the items listed freaks you out, click the Sign Out All Other Sessions button to do just that. In a flash, you're the only one accessing your account.

And then, immediately change your password. As in right now!

Preventing Phishing

Google is now checking any email that says it comes from paypal.com or ebay.com using a technology known as DomainKeys. If the email doesn't come from either of those two domains, it's rejected silently, behind the scenes, and you'll never even know a scammer was trying to trick you. That's fantastic and a great way to protect users.

Limiting How Many Emails You Can Send

To prevent spam and abuse, Google limits how many emails you can send a day. If you go over that limit, your account is temporarily suspended from sending mail.

If you're using the Standard Edition of Google Apps, you can send email to up to 500 addresses outside your domain each day. If you use the Premier or Education Editions of Google Apps, you can send mail to up to 2,000 addresses outside your domain each day. These email addresses can be anywhere in To, CC, and BCC fields.

What if you're an administrator? How do you send email to all your users if the total number of users is greater than the number of addresses to which you're allowed to send mail? Google suggests that you create multiple accounts, such as Admin1 and Admin2. If you do that, each account can send 500 messages, for a total of 1,000 if you're using the Standard Edition; the number is larger if you're using the Premier or Education Edition.

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