Attacks on computer systems

Sophisticated criminals are able to exploit vulnerabilities on computers and other devices. Some of the techniques they use include:

  • unauthorised access or hacking – when someone gains access to your computer or device without permission,
  • malware – malicious software (such as viruses, trojans and spyware) which monitor your online activity and cause damage to the computer,
  • denial of service attacks – an attack which floods a computer or website with data, causing it to overload and prevent it from functioning properly. This type of attack is more frequently targeted at businesses, rather than individuals.

Attacks can result in a criminal accessing your personal or financial details and can prevent you from being able to use your device or computer system properly.

These types of computer offences are covered by the Criminal Code Act 1995 (Cth). The Australian Federal Police website provides more information about high tech crime. States and territories also have laws dealing with computer related offences including attacks on computer systems.

In some instances, an attack on a computer system can be resolved by performing a scan of your computer using up-to-date anti-virus software. You may also wish to consider the steps outlined under Securing your computer to protect against further attacks. You can also report attacks on computer systems to the ACORN.

Unauthorised access

Unauthorised access or hacking is when someone gains access to your computer or device without permission. Hackers may gain access to your computer or device through security weaknesses, phishing or malware. Once they have compromised your email, banking or social media accounts, they can change passwords preventing you from accessing your accounts. Scammers often send out messages impersonating you directing people to fake websites, or asking them to send money.


Criminals may use malicious software (or malware) to monitor your online activity and cause damage to the computer. Malware is often downloaded when people open an infected email attachment or click a suspicious link in an email. Malware can also be used to steal your usernames, passwords or other information, which is then forwarded to a third party.

‘Malware’ is a catch all term to describe different types of malware which include viruses, worms, spyware, trojans or bots.

Case study

Anthony is a senior citizen from Bunbury, WA. Recently, he has noticed that his computer is running slowly. Pop-up advertising appears when he opens his browser and his home page has been changed. He is not sure what is happening, but suspects that his computer has a virus. He hasn’t raised the matter with his internet service provider or a family member. Before reporting to the ACORN, Anthony should scan his computer using up-to-date anti-virus software and consider contacting his internet service provider. More advice on preventing cybercrime can be found by reading about techniques for cybercrime prevention.

Denial of service or distributed denial of service attacks

A denial of service attack floods a computer or website with data, which can overload the system or computer and prevent it from functioning properly. Unlike hacking or malware, it generally doesn’t involve access to the computer system. A distributed denial of service (DDoS) attack is a denial of service attack that comes from multiple systems, often a network of compromised computers.

Case study

A real estate agency in Newcastle has suffered an attack on their corporate network which has left it inoperable. A database containing thousands of contact details of clients and detailed information on the properties listed for sale has been lost. If the agency cannot retrieve this information, it will take months and thousands of dollars to recompile the database. The real estate agency should report this on the ACORN and take steps to secure its computer network from further attacks.