Security firm Zvelo has discovered that the Google Wallet PIN, which is required of users to confirm purchases made with their phones, can be cracked via an exhaustive numerical search. Being able to access the PIN would allow criminals to use a Google Wallet-enabled phone to make purchases.
Because they're in the security business, Zvelo disclosed the issue to Google, which has confirmed that the vulnerability exists, and has "agreed to work quickly to resolve it."
Google Wallet is the first publicly available Near Field Communication (NFC) payment service in the U.S., and it's only available on one phone, on one network -- the Samsung Galaxy Nexus S 4G on Sprint.
NFC payment systems let users pay for items in brick-and-mortar retail stores by tapping their NFC-enabled device on a PayPass reader, or a small electronic box. NFC isn't limited to smartphones -- Google Wallet is partnered with MasterCard, which has been using NFC chips in some of its credit cards for several years, and which originally developed the PayPass reader.
There have been some questions about NFC security, and other wireless providers, such as AT&T, Verizon, and T-Mobile, currently do not allow the Google Wallet app on their smartphones. (Though this is probably because they're working on developing their own NFC payment system.)
However, because the Verizon Samsung Galaxy Nexus has NFC technology built-in, it is possible to install the Google Wallet app on that phone.