IP Addresses and Surveys

An IP address identifies the server the request comes from, not an individual computer. In the case of larger corporations and ISPs, it may represent merely the "gateway" or front door for a number of local or even geographically distributed systems.

So if you're doing a B2B survey, and send e-mail invitations to the Sales Manager and VP at one organization, when you use an IP address to prevent ballot box stuffing, you've just risked locking out one of those contacts. It's only a risk because we're an increasingly mobile surfing society, so while you may not be optimizing your questionnaires for iPhones and Blackberries, respondents could be completing forms from their:

• Home
• Office
• Commuter train
• Client site
• University library
• Favorite coffee house
• Airport terminal
• Hotel

Except for Home, each of those locations is node where a large range of individuals accesses the Internet, and—depending on your survey—multiple valid responses could be originating.

Those commonly accessed locations, like servers hosting Web sites, are likely to have somewhat permanent addresses, known as static IP addresses. Home connections will typically have dynamic IP addresses, and while they may not change with the breeze—it could be as rarely as when the subscriber's router is restarted, it's good to be aware consumer ones are potentially more transient.

So, you're getting the picture why using an IP to prevent ballot box stuffing may block legitimate folks at the same node, company or ISP from responding while leaving big holes for anyone who roves to double submit?

Keeping in mind the potential for respondents to be "out of place" when they answer the survey, let's look at the second common use: gathering additional information.

This takes advantage of a function called a Reverse DNS lookup. Domain Name Servers (DNS) are the keepers of Web addresses, and with the right software (you don't want do this manually) a Reverse DNS will zip through your IP addresses inquiring what about the domain for each one. If you like, you can also find out a few other details, such as the physical location, though Country is the most common and reliable data used.

The one gotcha with a Reverse DNS on surfer's IP addresses is that, unlike Web sites which want to be found, servers used to create surfing nodes don't necessarily care about turning on the porch light. For the domain/server name, you may get:

• No name beyond the IP
• The ISP providing the individual or company's connectivity
• A variant on a recognizable corporate domain, such as their mail server or an Intranet sub-domain
• A completely unrecognizable and inaccessible name which is fallow or used privately

Server administrators aren't going to set the virtual attack dogs on you if you show up with a standard Reverse DNS, it's just that an IP isn't designed to tell the demographic secrets of the universe about the surfer, and therefore they haven't published an address book for your convenience. And given the long history of spamming and phishing, if they had, it would have been yanked from public access years ago anyway.

So where's the IP address useful?

• You can use the lookup information in aggregate, just as for analyzing Website traffic logs, to see generally where in the world people are surfing from. It's just not a replacement for asking the Country field in an address block or if you care about precision.
• When respondents are heavily concentrated, it can cautiously be used to segment. One organization had to do a bit of damage control when they forgot to split their e-mail drop by employees and members, and likewise didn't ask that on the survey. The corporate IP served as a rough way to ID most of the employees for some reporting breakdowns—with serious qualifying footnotes.
• Or, if you have repeat respondents, such as from panels or Website members, IPs are commonly used to screen out the riffraff. Blacklists for Web (and e-mail) traffic are often IP based as those values are harder to play musical chairs with than text-based addresses.