My computer has slowed down or is behaving oddly
Slowness is far more often an ordinary cause than a security one. Storage that is nearly full, a browser carrying a dozen extensions, dust in the vents and updates waiting to install account for most cases. Work through those before assuming anything got in, and run a scan with the protection already included in your operating system rather than buying something in a hurry.
Why has my computer become so slow?
Short answer: in most cases because the machine has run out of a resource it needs — free storage, memory, or thermal headroom — rather than because something malicious is running.
Likely causes
The commonest single cause is a system drive with very little free space. Operating systems write temporary files constantly, and when there is nowhere to put them, every operation slows. The second is accumulated startup software: each program that adds itself to the startup list costs a few seconds and a slice of memory, and after three or four years there can be fifteen of them. The third is age combined with heat. A processor that cannot shed heat will deliberately reduce its own speed, and dust in a laptop vent is enough to cause that.
Memory matters too. A machine that was comfortable with its memory when it was bought may not be comfortable with the same amount after several years of software growing. If the slowdown appears when you have several applications and many browser tabs open, and disappears when you close them, memory pressure is the likely explanation rather than anything else on this page.
What to try first, at no cost
- Restart the machine fully, rather than closing the lid, and let any pending updates finish.
- Check the free space on the system drive, and clear space if it is below roughly a tenth of the total.
- Open the startup list and disable anything you do not need running from the moment you log in.
- Note whether the slowdown is constant or appears only under particular conditions, and write that down.
- Run a scan using the protection that is already part of your operating system.
When to ask for official help
If the machine has become slow suddenly, makes clicking or grinding noises, or reports drive errors, treat it as a possible hardware fault and get it looked at before anything else — a drive that is failing can take your files with it. For general, vendor-neutral guidance on keeping a personal device in good order, the Australian Cyber Security Centre publishes advice written for individuals and small businesses.
Where a paid product may or may not help
A paid security subscription does not add storage, memory or cooling, so it will not address any of the causes above. Some paid suites include tidy-up utilities, but the same tidying can be done with the tools already on the machine. The honest position is that this particular symptom is rarely a reason to buy anything.
Why is the fan running constantly?
Short answer: because something is keeping the processor busy, or because the machine cannot get rid of heat efficiently any more. Both are worth identifying, and the first is easy to check.
Likely causes
A single process consuming the processor will keep the fan at full speed indefinitely. That process is often perfectly legitimate — a search index rebuilding after an update, a cloud storage client synchronising a large folder, a video call, or a browser tab running something demanding. Less often, it is software you did not intend to install, including the kind that uses a machine's spare capacity for someone else's benefit. Physical causes are equally common: dust in the vents, a laptop sitting on a soft surface that blocks airflow, or thermal paste that has dried out on an older machine.
What to try first, at no cost
Open the task manager on Windows or Activity Monitor on macOS, sort by processor usage, and watch for a minute. If one process is consistently at the top, search for its name before doing anything to it; many alarming-looking names belong to the operating system. If nothing stands out but the fan stays loud, move the machine onto a hard flat surface, check that the vents are clear, and see whether the noise changes.
When to ask for official help
If the machine becomes too hot to rest a hand on, shuts down by itself under load, or the fan makes a rattling noise, stop using it for demanding work and have the cooling checked. That is a repair question rather than a security one.
Where a paid product may or may not help
If the process using the processor is genuinely unwanted software, a security product — the one already built in, or a paid one — is the right tool to identify and remove it. If the cause is dust or a blocked vent, no software of any kind will change the outcome.
Why is only my browser slow?
Short answer: because the browser is carrying more than it can comfortably handle — extensions, tabs, or a connection that is slower than you think.
Likely causes
Extensions are the usual culprit. Each one inspects pages as they load, and a browser with ten or twelve of them will feel noticeably heavier than one with two. Extensions that insert or block advertising do the most work of all. Beyond that, tabs left open for days hold memory, and some sites continue running in the background even when you are not looking at them.
Connection speed is often misattributed to the computer. Mobile broadband and fixed wireless both slow in the evening when more households are active, and a Wi-Fi signal that has to pass through two brick walls will be slower than the plan you are paying for. If pages load slowly but the machine is otherwise responsive, the connection is the better suspect.
What to try first, at no cost
- Open a private or guest window, where extensions are usually disabled, and see whether the same page loads faster.
- If it does, re-enable your extensions one at a time until the slowness returns, and remove the one responsible.
- Check whether the browser itself has a pending update; browsers update often, and an old one can be noticeably slower.
- Compare speed on another device using the same connection, to separate the browser from the network.
When to ask for official help
If the slowness is the same on every device in the house, it is a connection question for your internet provider rather than a computer question. If your provider's response does not resolve it, the Australian Competition and Consumer Commission publishes information about what consumers are entitled to expect from services they pay for.
Where a paid product may or may not help
Security software does not make a connection faster, and an extra layer inspecting web traffic can occasionally make browsing feel slightly slower rather than quicker. Where a paid product does earn its place here is in identifying an extension that was installed alongside something else without being noticed.
How do I tell whether storage is the problem?
Short answer: look at the free space on the drive the operating system is installed on. If that figure is small, you have found at least part of your answer.
Likely causes
Storage fills quietly. Photographs synchronised from a phone, video files, downloads never deleted, old system restore points and the files left behind by major updates all take space without announcing themselves. On machines with a small built-in drive, a single large game or a few years of photographs is enough.
What to try first, at no cost
Both Windows and macOS include a storage overview that breaks usage down by category, which is a faster way to find the problem than opening folders one by one. Empty the recycle bin or trash, which often holds more than people expect. Move large media files to an external drive or to cloud storage you already pay for, and remove local copies of files that are duplicated in the cloud. Uninstall applications you have not opened in a year.
A point worth knowing
Deleting files from a cloud-synchronised folder deletes them from the cloud as well, on every device signed in to that account. If the aim is simply to recover local space, look for the option that keeps the file online but removes the local copy, rather than deleting it outright.
When to ask for official help
If the drive reports errors or the operating system refuses to write files even after space is cleared, that suggests a hardware problem, and a technician should see it before you spend more time on software.
Where a paid product may or may not help
None of this is a security question, and no security subscription addresses it. Cleaning utilities sold for the purpose rarely find anything the built-in storage tools do not.
What does it mean if the machine restarts on its own?
Short answer: most often heat, power or a driver fault. It is one of the few symptoms that points more strongly at hardware than at software.
Likely causes
A machine that shuts down abruptly under load is usually protecting itself from heat or losing power. On a desktop, an ageing power supply produces exactly this pattern. On a laptop, a battery that has lost capacity can cut out when the processor demands a burst of power. A faulty graphics driver can also cause restarts, usually while watching video or playing a game. Scheduled restarts after updates are a separate and entirely normal thing, and they announce themselves beforehand.
What to try first, at no cost
Record when it happens: at rest, under load, at a particular time of day, or after a particular application opens. Install any pending driver and firmware updates from the manufacturer's support page for your exact model. Check whether the machine is set to restart automatically after installing updates, and whether the timing matches.
When to ask for official help
Repeated unexplained restarts justify a visit to a repairer, particularly on a machine more than four years old. Back up anything important first — an unstable machine is not a reliable place to keep the only copy of anything.
Where a paid product may or may not help
Security software plays almost no part in this symptom. It is worth running one scan to rule the question out, using what you already have, and then concentrating on hardware.
My security scan says nothing is wrong, but it still feels wrong
Short answer: a clean scan is good evidence, not proof, and the behaviour that is worrying you may have an ordinary explanation that a scan would never report.
Likely causes
A great deal of unwanted behaviour is not malicious software in the technical sense, and so is not reported as such. A browser extension that changes your search engine, a program bundled with a free download that adds advertising, a site you once allowed to send notifications — all of these are, strictly speaking, installed with permission, and a scan may pass over them. Equally, changed default applications, a modified home page or a new toolbar can all come from software you chose to install, with an option you did not notice.
What to watch out for
- Advice that tells you to install a second security product to check the first. Running two at once causes conflicts more often than it finds anything.
- Any page claiming to have scanned your computer from inside a browser tab. A web page cannot do that.
- Downloads offered as a "cleaner" or "optimiser" in response to a symptom. Reach for the tools already on your machine first.
What to try first, at no cost
Go through the browser's extension list, the list of installed programs sorted by install date, and the notification permissions, and remove anything you do not recognise or no longer use. Reset the browser's search engine and home page to what you want. Then restart and see whether the behaviour that bothered you persists.
When to ask for official help
If you believe an account rather than the machine has been affected — unfamiliar sign-ins, messages sent that you did not write — that is covered in more detail under links and attachments, and incidents can be reported to the Australian Cyber Security Centre through cyber.gov.au.
Where a paid product may or may not help
This is the situation where a paid subscription most often appeals: the built-in tool has reported nothing, and a second opinion with a support line attached feels worthwhile. Norton AntiVirus Plus is one paid product in that category; its features and price are set by the vendor and are only accurate on the vendor's own pages, so read those before deciding. Visit the Norton AntiVirus Plus websitePaid affiliate link. SteadyScope is paid a commission by the affiliate network that operates the link if you buy after following it; your price is the same either way.