Most companies in the IT and IT Services industry need to be very cautious about who they hire. There is a chance that much of the information you access could be confidential and harmful if put into the wrong hands, and they need to exercise caution when considering bringing on a new hire. Assure the interviewer of your willingness to comply with any form of background check they require. Exhibit professional transparency by sharing anything that might come up, providing context, and giving you a better chance of landing the job. Not being transparent would suggest you're hoping issues from your past won't come up, which speaks to a lack of integrity and disrespect for their resources and time. If you're not sure if something from your past would appear on a background check, research everything and anything that might, and see if any of those apply to you.