Cyber criminals can damage their victim's computer systems and data by changing or deleting files, wiping hard drives, or erasing backups to hide some or all of their malicious activity and tradecraft. By wiping, or "zeroing out," the hard disk drives, which overwrites good data with zeroes or other characters, the criminals effectively erase or alter all existing data, greatly impeding restoration. This sort of criminal activity makes it difficult to determine whether criminals merely accessed the network, stole information, or altered network access and configurations files. Completing network restoration efforts and business damage assessments may be also hampered.

The FBI and DHS encourage businesses and individuals to employ mitigation strategies and best practices such as.

• Implement a data backup and recovery plan to maintain copies of sensitive or proprietary data in a separate and secure location. Backup copies of sensitive data should not be readily accessible from local networks. 
• Regularly mirror and maintain an image of critical system files.
• Encrypt and secure sensitive information.
• Use strong passwords, implement a schedule for changing passwords frequently, and do not reuse passwords for multiple accounts.
• Enable network monitoring and logging where feasible.
• Be aware of social engineering tactics aimed at obtaining sensitive information.
• Securely eliminate sensitive files and data from hard drives when no longer needed or required. 

The US-CERT webpage at www.us-cert.gov hosts a wide range of tips, best practices, and threat information for business and home users.

Read more: US-CERT Current Activity