Posts Tagged ‘networking’

Techie Tip of the Week — Packet Sniffers

Friday, May 20th, 2011

Last week we talked about TCP/IP and how when data travels across the Internet, that it “hops” from node to node in little pieces called packets.

Be aware! When you do things on the Internet, if the method of transport is insecure (for example, if you are looking at a web page using http instead of https, or if you are sending email to an address that is outside of your local network), the packets that are sent may be intercepted along the route by a hacker. Your email, web page, or, perhaps more importantly, web cookie (complete with your credentials intact) may get intercepted by a maleficent user!

Special computer programs, known as Packet Sniffers or Packet Analyzers, are used to do just that. As the data flows across the network, the sniffer tool captures each packet and decodes the packet’s raw data, showing the values of various fields in the packet.

You’re particularly vulnerable to having your data intercepted if you use a wireless device over an unsecured wireless network.  WiFi networks have a range of about 100 yards; anyone within a football field of your wireless device could be reading your email or log into your Facebook, Yahoo! Mail, or other account by stealing the unencrypted cookie with your login credentials.

So, what can you do?

  1. Always use https any time you log into an account.
  2. Don’t use a service that uses https during the login part but then switches back to http after logging you in. By default, Facebook and Yahoo! Mail do this. With Facebook, you can change your settings so it will always use https (Account>Account Settings>Account Security>Secure Browsing). With Yahoo! Mail, your username and password are protected, but once you log in, it switches you back to http. Anyone with sniffer software installed could read your email as it’s being sent.
  3. Be careful when using unsecured wireless networks. Don’t log into accounts that only use http. Don’t send important emails. When using  one of the free wireless hotspots at a fast food restaurant, hotel, coffee shop, airport, or school (including Stanford), most likely it will be on an insecure wireless network. Anyone within a football field running a packet sniffer could easily steal your credentials and access your account.

Techie Tip of the Week – Networking basics (TCP/IP)

Friday, May 13th, 2011

Ever noticed those blinking lights  continuously blinking on the back of your computer? Ever wondered why they’re blinking, or what’s going on?

This week, we’ll talk about two of the basic protocols of Networking — the Transmission Control Protocol over the Internet Protocol (TCP/IP).

First off, a protocol is a set of rules that define how computers and other devices communicate with one another — the “language” that computers use to “speak with each other. The TCP/IP are the set of protocols that allow the Internet to work.

Basically, here’s what happens:

  1. The destination’s application (web browser, email application, etc.) communicates to the network software in its computer’s OS, which in turn makes a connection to the computer that houses the desired item (email, movie, web page, etc.).
  2. Assuming the sending computer approves the sending of the information, the sending computer’s Transmission Control Protocol (“TCP”) takes the information to be sent and chops it up into little pieces (“packets”).
  3. These Internet Protocol (“IP”) packets are given address information, and, using the IP, they sent off to their destination.
  4. Each packet then “hops” from computer to computer (“node” to “node”), asking each node if they are at the final destination yet. If so, they wait for the other packets to arrive; if not, they hop to the next node until they finally reach their destination.
  5. Once all of the packets make it to the destination, they are reassembled back into the original item using the destination’s TCP.

This is similar to how moving a houseful of items works.

Let’s say you’re moving all of your belongings from one house in one city to another house in a different city. You would most likely take all of your possessions and put them into many different boxes. Then, after applying a label with your new address on it, you’d take each box to the shipping company. The shipping company then takes the package, and sends it off with all the other packages going to the same region. You never know exactly which direction the package may go – there might be a tornado in the northern part of the country, so the package might go the southern route; there might be a hurricane in the southern route, so the package may go the northern route. But each package continues on its way until it reaches the destination. And, until all of the packages arrive, you won’t have all of your items. But once you do, you could reassemble your entire houseful of possessions in your new place.

Graphical representation of how TCP/IP works

Next week, we’ll talk about some of the tools people use to track and “sniff” these IP packets as they’re traveling across the Internet.