Good to leave your Wifi open?

There's a lot of buzz lately about Bruce Schneier's new essay on how great it is to run an open wireless network at home. My take on this is going to be short and sweet: You're crazy if you leave your wifi open. Here's what can or will happen if you don't secure your wifi:
  • Your own download speeds suffer as neighbors' infected laptops find a new vector to spew spam and malware.
  • You'll find your home IP address blacklisted and receiving spam complaints over bad stuff people send via your connection.
  • The buck stops with you. Your ISP can trace it as far as you and no further. This means that if somebody uses your wifi network to send spam, or traffic in kiddie porn, you're the one whose door the feds or the FTC are going to knock on.
  • Running a mail server? You'll get blacklisted due to all of the above.
When I lived in Minnesota, I inadvertently left my wifi access point unsecured for a period of time -- and I did find mail server blacklisted. A neighbor's infected laptop used my connection to send spam. I was pretty embarrassed about it at the time -- an anti-spam guy's IP address was being used to send spam! It just highlighted for me how it's not wise to tempt fate. It might be really neat to leave your car unlocked, with the keys inside, so your neighbors can borrow it as needed. But, is it wise? C'mon, people!


  1. Most wireless routers let you block specific ports, so you can shut off outbound port 25 access except from hosts you trust to send email. You definitely don't want open port 25 on any open wireless network.

    I usually don't leave my network open mostly because I don't want to share bandwidth, but sometimes I open it when I have guests since it is less hassle that way.

  2. It doesn't stop from somebody parking in front of your house and creating a Yahoo account to send death threats to the presidents. The trail is going to lead back to your IP, and it'll be your door that the secret service knocks on.

    It doesn't stop somebody from using a P2P client or IM client to send objectionable/illegal content that you probably would prefer not to be associated with.

  3. I guess I agree with Bruce.

    I'd say my comfort level would vary depending on where I lived. Bruce lives in a rather quiet residential area. Folks in apartments in urban areas (or even houses) would probably want to be more careful. Risk goes up in higher traffic areas, would be my guess. Also more likely to have people use your bandwidth.

  4. I also live in a quiet residential/suburban area and we routinely see people driving around slowly trying to find a wifi signal they can use. I know of 2 instances in the last year that the police were called on because of people doing this.

    I tend to agree with the why risk it option. You can't be home all the time to report people who might be doing this.


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