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Should your modem stay on all the time? Is it safe from viruses if left on?

Let's be clear that we're talking about dial-up modems. By definition broadband modems are connected all the time.

In fact, if you think about it, a dialup modem that's always connected is pretty much just a really slow broadband modem.

Sort of.

I will clarify that by "on" you mean connected. It's certainly ok to leave your modem powered on at all times, whether or not you have dialed in. Dialing in and connecting to the internet is where the issues are.

You can certainly can leave it connected all the time if your ISP is ok with that. Many ISPs are not, and will drop the connection automatically after some period of inactivity. There are tricks you can play, of course, but those may well violate the terms of service with your ISP. So definitely check with them before staying connected continuously.

If you do stay connected for long periods of time, you should start thinking like a broadband user. That means taking all the precautions that a broadband user would take, including a firewall of some sort. Normally those steps aren't as important for dialup users because the connections are typically of a shorter duration. You're never 100% safe, but shorter connections mean fewer opportunities for infection and other problems.

So go ahead and connect, if you're allowed, and simply take the extra precautions of a firewall, and of course, up to date virus protection.

Article C2349 - May 11, 2005 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

May 12, 2005 5:50 AM

One concern about leaving a modem "on" (vs. "connected") that I would add is that, sometimes, a user has unknowlingly installed some dialer software which may dial a toll number during the middle of the night or anytime. So, take Leo's advice about ensuring your virus protection is up-to-date very seriously.

November 29, 2007 10:50 PM

hey there guys.

I was wondering, besides viruses, can you become infected with any type of tracking program if your modem is left connected and idle even with a firewall?

I was once told that even with a firewall there are still a number of ports through your modem that items can bypass by disguising itself as recognisable software/scripting (namely Active X)

What I mainly want to know is what other risks do I leave myself open to by not disconnecting my modem? OH yes, it's a dsl modem, and my ISP here does allow continuous use.

your advice and tips would be greatly appreciated.

P.S. I ask this because my family can never seem to turn off/disconnect the modem when they are finnished using the computer. they shut the comuter down to standby, but I am still worried that something can happen.

:) -dave

Leo A. Notenboom
November 30, 2007 12:54 PM

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So to be clear, the modem's I'm talking about above are dial-up. It's quite
standard for DSL connections to be on 24/7.

With a properly configured firewall (or in the case of broadband like DSL, a
good NAT router), the only things that can enter your computer are things that
your computer *asks* for. By that I mean that incomming connections are blocked
by the firewall, but that doesn't prevent malware on your computer from going
out and downloading something on your behalf.

That's true no matter how you're connected to the internet, or for how long.
And it's why it's so incredibly important to prevent malware from infecting
your machine by having anti-spyware and anti-virus software, and to not run
attachments or other downloads you don't trust.



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