I assume you have run a complete scan of your system with your A/V software to look for malware? And change your password right away if you haven't already. As for the address book, call Comcast security and see if they can restore it for you------------------
Comcast Customer Security Assurance-------------------
Normal business hours (6:00 am to 2:00 am EST, 7 days a week)
1 - 888-565-4329
The same thing happened to me. Here are directions on how to retrieve your address book, but it is a tedious process, so make sure you have a lot of time. It took me 5 hours and 2 days to do this. Good luck.
I have WINDOWS 10:
To into either Google Chrome or Firefox. Other browsers might not work. Bring up another browser (anyone but Firefox or Google Chrome). You'll be working with two browsers. On G.C. or F. , type in www.icloud.com. Sign into Cloud with your Apple ID and press on the ENTER key on your keyboard. Put in your Password of Apple ID. **Click on Contacts icon. Highlight about 5 or 10 names. In the bottom left corner of teh scree, there is a "round gear". Click on it. Click on Export V card from the menu.. If you look across the top of teh screen, you should see an arrow pointing downward to a line. Click on that arrow and you will see the file that this download has made.
Now use your other browser and click on the Address Book or Contacts. Aat the bottom of the left column, you'll see "Import Contacts". Click on that, and GET STARTED when that pops up. Click Contacts, then File. Your Downloads screen will appear. Click on the file you want to put into your Address Book or Contacts list. Then click OPEN. A screen should come up asking you to login to your mail account. DO NOT CLICK on anything. Just let this screen sit there. Go back to your other browser. You should be able to get back to your mail account by clicking on the tab at the top left of your screen. If it is not there, you need to get back to your mail account some other way. SIGN OUT of your mail account, then sign back in.
Now go back to the other browser and click on "Login to destination of your mail account" A circle should begin to rotate, and another screen willl pop up in a few secons telling you the file is going into your address book. Then click on "Go back to your Address Book" and see if the file is there.
Note: if the rotating circle doesn't stop in a bout 30 seconds and take you to the next screen, one of the names in the file you have chosen is corrupted. To find out which one is corrumpted, go back to the double asterisk (**) and follow the directions from there, but only download one name at a time, then look at your downloadlist to see which one(s) aren't in the files. Then, go back and highlight all the ones that did download, and try again. This is why I said, only do 5 or 10 names at a time. Sometimes the entire 10 will download, sometime not.
Note 2: if you click on the "geared wheel" (lower left corner) and an error message comes up, go to the "arrow pointing down to the line" (upper right of screen) and click on it.Your file might hae been downloaded anyway. You be able to see it in the popup. Proceed from there.
As you can see, this is a very slow process. Take your time and do it a little at a time. Good luck.