The computer might be compromised if its physical components have been altered.For example, if a keylogger has been physically installed on the computer, your passwords, personal information, and other data typed on the keyboard could be stored and accessed by someone else, even if you are using Tails.
Use the [[screen keyboard|doc/first_steps/accessibility#keyboard]], if you are using a public computer or worry that the computer might have a keylogger.
Keyloggers are easy to buy and hide on desktop computers but not on laptops. For an example, see <a href="https://www.youtube.com/watch?v=6JJo8qCYE8M">KeeLog: KeyGrabber forensic keylogger getting started</a>.
Firmware attacks have been demonstrated, but are complicated and expensive to perform. We don't know of any actual use against Tails users. For an example, see <a href=https://www.youtube.com/watch?v=sNYsfUNegEA>LegbaCore: Stealing GPG keys/emails in Tails via remote firmware infection</a>.