What Malware Does

Malware is software written to harm a computer, the data stored on it, or the person using it. Once it is running on a device it can carry out whatever it was written to do, and it may do several of these things at once.

Effect	What it means
Delete or corrupt files	Files are removed or damaged so they will not open. Documents, music or saved games can be lost for good.
Change data	Details are altered without you noticing. A wrong date in a project plan or a changed score in a spreadsheet can cause problems later.
Copy and steal data	Malware sends copies of files or account details to someone else, so private information is no longer private.
Lock or encrypt files	Files are made unreadable or blocked, so even you cannot open them. This stops you using your own work.
Spy on activity	It records what you type, the sites you visit or the messages you send, watching what you do without permission.
Slow down or crash the computer	It uses up processing power, memory or storage, so programs lag, or the device freezes and stops responding.
Allow remote control	An attacker can operate the computer as if they were sitting at it, opening files, running programs and changing settings.

These effects can happen together. A tablet used for homework and for editing videos could have its saved videos corrupted, its project file changed, a folder of half-finished videos copied to someone else, its whole homework folder locked and its browsing history read, all by the same piece of malware. The tablet might also slow to a crawl and let an attacker open apps on it remotely. Damage like this can be permanent: deleted files may not be recoverable and changed data may go unnoticed.

Practise this