Is It Safe to Buy a Used Modem or Router? Check Its Age First

Yes, a used modem or router is usually safe to buy, as long as its maker still sends it security updates. That one detail matters more than scuffs, the box or the price. The FBI has warned about worn-out routers twice in just over a year. In May 2025 it said criminals were taking over old routers and renting them out as hiding places for their own traffic. In April 2026 it said a foreign intelligence service had quietly changed the settings on vulnerable home routers to steal passwords. In both alerts the advice was the same: replace a router its maker no longer supports.

A used router is only as safe as its last update. Check that first, then the price.

The good news is that every check below takes a few minutes. Most of them need nothing but the model number on the sticker underneath.

Why does the age of a used router matter so much?

A router sits between every phone, laptop and smart speaker in your home and the rest of the internet. When the company that made it stops releasing fixes, any weakness found afterwards stays open for good.

The FBI's May 2025 alert said routers from 2010 or earlier probably no longer get software updates, so attackers can break in through flaws that are already public. It described a piece of malware called TheMoon. It does not need a password. It looks for open doors on old routers, gets in, then searches for more victims. The criminals behind it sold the hijacked routers as "proxies", so their crimes looked like they came from someone else's home.

The April 2026 alert was about a different group, Russian military intelligence, but the weak spot was the same. The attackers changed the router's address-book settings (called DNS), and every device on the network picked up the poisoned settings automatically. That let them steal passwords and email from people who clicked past a browser's certificate warning.

Neither alert is about used routers as such. A router you bought new in 2015 carries the same risk as one bought secondhand yesterday. A used router is a problem only when it is an old one that its maker has stopped supporting.

What should you check before buying a used router?

Use this list at a yard sale, an online listing or a liquidation pickup. Ask the seller for the model number, or a photo of the label, before you go.

1. Look up the model on the maker's support page. Search for the model number with "end of life" or "end of support." If it is on that list, walk away, however cheap it is. Both FBI alerts tell owners to replace unsupported routers.
2. Check the newest firmware date on the same page. Firmware is the router's built-in software. A recent release is a good sign. A last update from years ago is a warning.
3. Check the Wi-Fi security it supports. The FTC says to use WPA3 or WPA2. If a router offers only WEP or plain WPA, the FTC suggests thinking about a newer router.
4. Check your provider's list before you pay (for modems). Xfinity says a device that is not supported "won't work" on its service, and it asks you to check compatibility for your address before buying. Other providers have similar pages. A cheap modem your provider will not activate is no bargain.
5. Make sure it matches your speed. Xfinity notes that its gigabit plans need a device that can handle gigabit speeds. An older modem may work but cap what you pay for.
6. Make sure the power adapter is included and correct. The right voltage is printed on the router's label. Do not swap in a random charger from a drawer.

What should you do the moment you plug it in?

Do these before you connect a single phone or laptop. They come from the FTC's home Wi-Fi guide and the FBI alerts.

The FBI's 2025 alert asks for passwords of 16 to 64 characters, unique and random. A short sentence made of four or five unrelated words is easy to type and hard to guess.

One limit worth knowing: a factory reset clears the old owner's settings, but it cannot make the maker start sending updates again. If the model is past end of support, a reset does not fix that.

Which warning signs mean a router may have been tampered with?

The FBI's 2025 alert lists three signs of a router that may already be taken over:

• It runs hot even when nobody is using the internet much.
• The connection keeps dropping or slowing for no clear reason.
• Settings have changed that you did not change.

If you see these on a router you just bought, reset it, update it and change the admin password. If they come back, stop using it. The FBI asks people who think they were targeted to report it at ic3.gov.

For anything else you buy secondhand that connects to the internet, the same idea applies. Our factory reset checklist for smart devices walks through cameras, speakers and doorbells.

Is a used modem different from a used router?

Yes, in one useful way. A modem is the box that talks to your internet provider over the cable or phone line. A router shares that connection around your home and runs your Wi-Fi. Many homes have one box that does both.

A modem's main hurdle is your provider, not hackers. Your provider has to recognise and switch on the device, so check its list first, as in step 4 above. A separate router is more flexible. Xfinity, for example, says customers in its fibre communities can use any standard router that matches their speed tier.

That makes a used router the easier buy for most people in the DC, Maryland and Virginia area. Keep the modem your provider supports, and add a newer secondhand router behind it.

Is it worth buying an open-box or returned router?

Often it is. Many returned routers come back because they did not suit the buyer's home, not because they broke. The checks are the same as for any used one: model, support status, firmware, reset. Our guide to open box vs refurbished vs used explains what each label is supposed to mean.

If you are browsing electronics on DealsDMV, look up the model number before you bid in auctions or buy in Buy Now, and see the FAQ for how pickup and payment work.

The bottom line

A used router or modem is not risky because someone else owned it. It is risky when it is old enough that its maker has stopped fixing it. Check the model, check the support status, then reset and update it before you trust it with your passwords. Do that, and a secondhand router can be one of the easiest savings in a home tech budget.

Know someone about to plug in a hand-me-down router? Send them this checklist first.