
Some two thirds of popular iPhone apps transmit users UDIDs, leading to  potential security concerns, a new study has warned. 
Eric Smith, Assistant Director of Information Security and Networking at Bucknell University in Lewisburg, Pa.,  discovered 68 percent of the 57 top applications in the App Store sent out UDID  information, back to a remote server, owned either by the application developer  or an advertising partner.
 Those popular iPhone applications tested included those from Amazon, Chase  Bank, Target, Sams Club, Best Buy, Barnes & Noble, eBay, PayPal, Bank of  America, Wells Fargo, Fidelity and American Express.
 UDIDs, or unique device identifiers, are a 40-digit sequence of letters and  numbers, and can be used to identify users and transmit sensitive information,  unencrypted and to third parties.
 Smith warned that popular applications such as those from Amazon, Facebook or  Twitter inherently have the ability to tie a UDID to a real-world identity.  “Most iPhone application vendors are collecting and remotely storing UDID data,  and some of these vendors also have the ability to correlate UDID to a  real-world identity,” Smith said.
 “For example, Amazon’s application communicates the logged-in user’s real  name in plain text, along with the UDID, permitting both Amazon.com and network  eavesdroppers to easily match a phone’s UDID with the name of the phone’s  owner.”
 Smith noted in conclusion: “Privacy and security advocates, personal iPhone  owners, and corporate iPhone administrators should be concerned that it would be  feasible—and technically, quite simple—for their browsing patterns, app usage,  and physical location collected and sold to unintended customers such as  advertisers, spouses, divorce lawyers, debt collectors, or industrial  spies.”
 “Since Apple has not provided a tool for end-users to delete application  cookies or to block the visibility of the UDID to applications, iPhone owners  are helpless to prevent their phones from leaking this information.”
 Apple’s mobile platform is not alone in being open to potential abuse.  Researchers at Duke University, Pennsylvania State University and Intel Labs discovered only last  week that many applications on Google’s rival Android platform were sending  information, such as users GPS location and phone numbers, without the knowledge  or permission of the user.
 Smith’s full study, iPhone  Applications & Privacy Issues: An Analysis of Application Transmission of  iPhone Unique Device Identifiers (UDIDs), is available as a PDF.
 Smith, author of the study, is a founding member of PreSet Kill Limit, the  security research group which has won the Defcon Wardriving hacking contest  several years in a row.