Feeds

Crap PINs give wallet thieves 1-in-11 jackpot shot

What are the odds? Cambridge boffins work it out

Choosing a cloud hosting partner with confidence

Four-digit banking PINs are almost as insecure as website passwords, according to a study by Cambridge University computer scientists.

The first-ever quantitative analysis of the difficulty of guessing four-digit banking PINs estimates the widespread practice of using a date of birth as a PIN code and other factor means that opportunistic thieves will be able to correctly guess a PIN before a card is blocked between 8-9 per cent of the time.

The researchers modeled banking PIN selection using a combination of leaked data from non-banking sources (smartphone unlock-codes and the RockYou dataset) and an online survey. The 1,300 people quizzed online were not asked for their PIN, only if it fell into one of the general categories the Cambridge University team identified.

Most people are significantly more careful choosing PINs than online passwords, with a majority using an effectively random sequence of digits. However a few weak choices – and using birthdays in particular – provide hope for opportunistic thief.

In a blog post, Cambridge University researcher Joseph Bonneau explains:

About a quarter stick with their bank-assigned random PIN and over a third choose their PIN using an old phone number, student ID, or other sequence of numbers which is, at least to a guessing attack, statistically random.

In total, 63.7 per cent use a pseudo-random PIN, much more than the 23 to 27 per cent we estimated for our base datasets. Another 5 per cent use a numeric pattern (like 4545) and 9 per cent use a pattern on the entry keypad, also lower than the other two datasets.

Altogether, this gives an attacker with six guesses (three at an ATM and three with a CAP [hand-held card] reader) less than a 2 per cent chance of success.

Unfortunately, the final group of 23 per cent of users chose a PIN representing a date, and nearly a third of these used their own birthday. This is a game-changer because over 99 per cent of customers reported that their birth date is listed somewhere in the wallet or purse where they keep their cards. If an attacker knows the cardholder’s date of birth and guesses optimally, the chances of successfully guessing jump to around 9 per cent.

If customers use their wallet then it is very likely to have a ID document with a birth date printed on it. That makes choosing a date of birth for a bank card PIN a terrible idea. Other not-so-random codes include PINs representing dates, years, repeated digits, ascending digits or ending in 69. More bad practices in the area include sharing and reusing PINs.

The researchers suggest that blacklisting the top 100 PINs can drive the guessing rate down to around 0.2 per cent in the general, though not if a user's birthday is known, where the rate stays at 5 per cent. Dropping all dates that can be considered as birthdays doesn't work because there are too many.

Even so, some blacklisting can be done. Shamefully some banks in both the US and Europe fail to prohibit obviously guessable PINs, such as 1234, the Cambridge boffins report.

The team's research paper, A birthday present every eleven wallets? The security of customer-chosen banking PINs – by Joseph Bonneau, Sören Preibusch and Ross Anderson, can be found here (PDF). ®

Internet Security Threat Report 2014

More from The Register

next story
FYI: OS X Yosemite's Spotlight tells Apple EVERYTHING you're looking for
It's on by default – didn't you read the small print?
Russian hackers exploit 'Sandworm' bug 'to spy on NATO, EU PCs'
Fix imminent from Microsoft for Vista, Server 2008, other stuff
Edward who? GCHQ boss dodges Snowden topic during last speech
UK spies would rather 'walk' than do 'mass surveillance'
Microsoft pulls another dodgy patch
Redmond makes a hash of hashing add-on
NOT OK GOOGLE: Android images can conceal code
It's been fixed, but hordes won't have applied the upgrade
'LulzSec leader Aush0k' found to be naughty boy not worthy of jail
15 months home detention leaves egg on feds' faces as they grab for more power
China is ALREADY spying on Apple iCloud users, claims watchdog
Attack harvests users' info at iPhone 6 launch
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Three 1TB solid state scorchers up for grabs
Big SSDs can be expensive but think big and think free because you could be the lucky winner of one of three 1TB Samsung SSD 840 EVO drives that we’re giving away worth over £300 apiece.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.