It’s Safer to Write Your Password Down

By Gunter Ollmann

Common wisdom over the last couple of decades has been to never write down the passwords you use for accessing networked services. But is now the time to begin writing them down? Threats are constantly evolving and perhaps it’s time to revisit one of the longest standing idioms of security – “never write a password down”.

Back in the day, a password was a critical part of the corporate identity system. You supplied your user ID and password pair in order to get online and to access key corporate resources. Access controls then extended the authentication model to enable greater control of what users could see, do and change. As new systems came online, and as business extended beyond the in-house corporate networks, additional (i.e. separate) authentication systems came in to play. Despite multiple attempts at developing and deploying single sign-on (SSO), most employees still need to juggle a dozen passwords in order to do their work. If they have external Internet accounts as well, then they’ll be juggling several dozen additional passwords. Once you thrown in their personal Internet accounts (webmail, Twitter, Facebook, LinkedIn, PayPal, Amazon, etc.) you’re quickly neck-deep in password soup.

What’s traditionally been the problem with writing down password anyway? Well, since passwords are the critical ingredients for access control, corporate security teams have long “educated” employees in to never writing them down. To do so would potentially expose yourself to impersonation – and you’d ultimately be responsible for whatever (damage) the impersonator did in your name.

In the meantime, Internet guides, popular PC magazines, and practically every website that forces you to create a login account, all extol the virtues of never writing your passwords down. They also give you lots of additional advice – such as “use a strong password”, “use a unique password”, “never use the same password on a different site”, etc. All of which make it incredibly difficult for any practically minded human to keep track of which password belongs to which website. The net result being that the “password rules” are being repeatedly broken.

Now, to ease some of this burden, there have been spurts of software tools that’ll help remember passwords on your behalf. For example, the popular web browsers all provide some capability in this area. The problem though is that the bad guys have better tools. Practically all of today’s malware(along with all those botnets you hear about each day) have the built-in capabilities of grabbing/stealing both the passwords you’ve remembered and type in each time you visit a favorite website, and the passwords being conveniently “remembered” by the software on your computer.

Why would writing down a password be good? Well, it’s not a question of being good – just better. Granted, anything you type on your computer can (and will) be grabbed by the malware it’s been compromised with- but the lowest hanging fruit for the bad guys lies with all the stuff you’ve already asked your computer to remember on your behalf. After 3 months of use, web browser “remember” functions may have captured 50+ sets of authentication details. Within a few seconds of computer compromise, all three moths worth of stored credentials will have been copied and stolen (oh, and they’re neatly formatted and sorted) – so the malware doesn’t need to do any work, and it doesn’t matter if your anti-virus software gets an update tomorrow capable of detecting the malware and removing it. The damage is already done.

Staying hidden on a victim’s computer is not a trivial task for many malware – particularly wide-spread Internet malware (anything with a name you may have read about). There are lots of things that can go wrong. AV updates may detect the infection, dropper websites may be taken down, uploading sites may be sinkholed, CnC domains may be hijacked, etc. so it’s become important for modern malware to steal as much information as possible within the shortest possible time. Factors such as conveniently storing all your authentication details on your computer and recycling popular (i.e. memorable) passwords reduce the time the malware needs to be operating in order to steal critical data.
What about a few high-level odds?

• 1:3 – home PC being infected with malware with password stealing capabilities in a given year.
• 1:4 – home PC being infected with a botnet agent in a given year
• 1:8 – corporate PC being infected with malware with password stealing capabilities in a given year
• 1:12 – corporate PC being infected with a botnet agent in a given year
• 1:160 – your car being stolen in a given year
• 1:700 – your home being burgled
• 1:600,000 – being struck by lightning

I think it’s time to revisit the “never write a password down” idiom. Prioritizing best practices in password management, I’d be inclined to list them in the following order:

1. Don’t use the same password on multiple websites
2. Don’t let your computer “remember” your password!
3. Use a “strong” password – preferably something with 12+ mixed characters
4. Don’t use a predictable algorithm – e.g. abc123
5. Change your passwords regularly. For sites with lots of personal information and associated monies, change every 2-3 months. For other sites, try every 6-12 months.
6. Don’t reuse past passwords – even if you think it’s a cool password.
7. Don’t write your password down.

Yes, that’s right – writing down your passwords come in at a distant 7th place. In practical terms, even if you only manage the first 4 on the list, you’re probably going to be juggling at least a couple of dozen passwords (or more thank likely that’ll be 40+ on a regular basis for most people that spend any time online). The probability that your computer(s) will be compromised and that the information will be stolen by the bad guys malware is much, much greater than the probability that someone will manage to break in to your house and target all the post-it notes you’ve stuck around your screen with all your passwords on them. In corporate environments there’s a higher probability that the evening cleaning crew would gain visibility of he passwords (so post-it notes aren’t to be recommended), but that risk of an insider threat is still going to be lower than your work computer being compromised.

The first 6 password recommendations would trump the 7th in most cases – provided you take care in how and where you write your passwords down. Be smart about it… but don’t underestimate the risks posed by modern malware either.