When a breach is first discovered, your initial instinct may be to securely delete everything so you can just get rid of it. However, that will likely hurt you in the long run since you’ll be destroying valuable evidence that you need to determine where the breach started and devise a plan to prevent it from happening again.
Instead, contain the breach so it doesn’t spread and cause further damage to your business. If you can, disconnect affected devices from the Internet. Have short-term and long-term containment strategies ready. It’s also good to have a redundant system back-up to help restore business operations. That way, any compromised data isn’t lost forever.