network icon is lit up all the time even when no net-accessing application such
such as IE, Yahoo Instant Messenger, MSN Instant Messenger and the like are running. Does
the light being on all the time like that mean I’ve been infected with
That’s a definite maybe.
There are a lot of things that cause network activity when you’re not using
your machine. Depending on how your machine is configured, and how it’s
connected to the internet, some of that network activity could definitely be
bad and lead to an infection, if you’re not already infected.
On the other hand, it could also be a sign of things working properly.
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The internet is a scary place. Nothing shows that more than watching the
network traffic on an unprotected internet connection. Unprotected machines are
under a constant barrage of automated hacking attempts, viruses attempting to
propagate, and all sorts of other bad things. It’s actually quite sobering to
watch if you have the setup to do so.
Depending on your connection to the internet, if you’re not behind something
that protects you from them, all that constant network activity could easily be
the constant noise of attempts to compromise your machine.
This is why you must have a firewall.
If you have a hardware firewall, such as a router, your computer will simply
not see any of this – all those probes and attacks won’t make it to you. If
you’re running a software firewall, this internet noise may make it to your
machine (and hence may light up your network icon), but will be blocked by the
Either way, a firewall is key.
If you are infected with a virus or spyware, then absolutely, that could be
sending out a lot of network traffic. In fact, one of the most common concerns
across the internet right now are machines that are infected and used to sent
massive amounts of spam. These machines, so-called ‘bots’ or ‘zombies’, are
ordinary machines that have been infected with software that can be controlled
remotely. While the most common use is to send out massive amounts of spam,
another is to participate in “distributed denial of service”, or DDOS attacks
on other machines, sites or servers. In either case, this type of activity
results in a lot of network activity, and yes, could cause your network icon to
remain lit constantly.
The lesson there: make sure you’re running up to date anti-virus and
If you’re not running a program that explicitly access the internet, then
constant activity is rare. But there are things that can cause prolonged
The one that I keep forgetting about (until my DSL connection slows down) is
automatic updates. Depending on your configuration, Windows Automatic Updates
could, perhaps, be downloading the latest updates for your machine. In fact, any
software package that has a “check for updates” feature could be doing
something like this.
If you’re still unsure of what’s going on, there are some utility programs
that may help. My earlier article How
can I tell what internet activity is happening on my machine? mentions
several tools that will let you examine what internet connections and activity
your machine may have.