If this ink marks are on the casing, don't use an abrasive as that will scuff the casing. Instead, turn off the computer, get some rubbing alcohol, dabble it on a folder paper towel, and wipe down the casing with some force. It may take a few applications. Make sure you don't soak the paper towel. Just make sure it's moist. The last thing you want is the rubbing alcohol to run into the electrical components.