1. A computer ( ) attaches itself to a program or file so it can spread from one computer to another, leaving infections as it travels. Almost all ( )es are attached to an executable file, which means the ( ) may exist on your computer but it cannot infect your computer unless you run or open the malicious program. It is important to note that a ( ) cannot be spread without a human action to keep it going.

• 1
  virus

---

• 2
  deadlock

---

• 3
  Hacking

---

• 4
  Netizen