I am not a tax pro so don't take my answer to the auditor or your CPA....
It is my understanding that you can write off the percentage of a thing you used for business. So if you are using your internet once a week for business and you use it once a week the equal amount for personal stuff, then you could write off 50%. Or if you were using it once a week for 30 minutes for business and every day 8 hours a day for games and videos and .......... I doubt you could justify writing it off.
But thats just my opinion.........
The previous response is correct - it is deductible, but only to the extent you actually use it for business purposes.
The IRS requires the expense to be a usual, necessary, customary and reasonable for your type of work. So, you could argue that you meet that test. However, in order to take the deduction, you must have maintained a written log detailing business use and personal use of the internet in your home. The log should include date, business purposes, and time spent on the task. It should also include the same for personal use.
Honestly, if you are only using it for one task once per week, the percentage of business use wouldn't be worth the time necessary to maintain a log that will meet IRS audit standards.