Security Engineering. Ross Anderson
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[813].
Phishing attacks against banks started seven years later in 2003, with half-a-dozen attempts reported [443]. The early attacks imitated bank websites, but were both crude and greedy; the attackers asked for all sorts of information such as ATM PINs, and their emails were also written in poor English. Most customers smelt a rat. By about 2008, the attackers learned to use better psychology; they often reused genuine bank emails, with just the URLs changed, or sent an email saying something like ‘Thank you for adding a new email address to your PayPal account’ to provoke the customer to log on to complain that they hadn't. Of course, customers who used the provided link rather than typing in www.paypal.com or using an existing bookmark would get their accounts emptied. By then phishing was being used by state actors too; I described in section 2.2.2 how Chinese intelligence compromised the Dalai Lama's private office during the 2008 Olympic games. They used crimeware tools that were originally used by Russian fraud gangs, which they seemed to think gave them some deniability afterwards.
Fraud losses grew rapidly but stabilised by about 2015. A number of countermeasures helped bring things under control, including more complex logon schemes (using two-factor authentication, or its low-cost cousin, the request for some random letters of your password); a move to webmail systems that filter spam better; and back-end fraud engines that look for cashout patterns. The competitive landscape was rough, in that the phishermen would hit the easiest targets at any time in each country, both in terms of stealing their customer credentials and using their accounts to launder stolen funds. Concentrated losses caused the targets to wake up and take action. Since then, we've seen large-scale attacks on non-financial firms like Amazon; in the late 2000s, the crook would change your email and street address, then use your credit card to order a wide-screen TV. Since about 2016, the action has been in gift vouchers.
As we noted in the last chapter, phishing is also used at scale by botmasters to recruit new machines to their botnets, and in targeted ways both by crooks aiming at specific people or firms, and by intelligence agencies. There's a big difference between attacks conducted at scale, where the economics dictate that the cost of recruiting a new machine to a botnet can be at most a few cents, and targeted attacks, where spies can spend years trying to hack the phone of a rival head of government, or a fraudster can spend weeks or months of effort stalking a chief financial officer in the hope of a large payout. The lures and techniques used are different, even if the crimeware installed on the target's laptop or phone comes from the same stable. Cormac Herley argues that this gulf between the economics of targeted crime and volume crime is one of the reasons why cybercrime isn't much worse than it is [889]. After all, given that we depend on computers, and that all computers are insecure, and that there are attacks all the time, how come civilisation hasn't collapsed? Cybercrime can't always be as easy as it looks.
Another factor is that it takes time for innovations to be developed and disseminated. We noted that it took seven years for the bad guys to catch up with Tony Greening's 1995 phishing work. As another example, a 2007 paper by Tom Jagatic and colleagues showed how to make phishing much more effective by automatically personalising each phish using context mined from the target's social network [973]. I cited that in the second edition of this book, and in 2016 we saw it in the wild: a gang sent hundreds of thousands of phish with US and Australian banking Trojans to individuals working in finance departments of companies, with their names and job titles apparently scraped from LinkedIn [1299]. This seems to have been crude and hasn't really caught on, but once the bad guys figure it out we may see spear-phishing at scale in the future, and it's interesting to think of how we might respond. The other personalised bulk scams we see are blackmail attempts where the victims get email claiming that their personal information has been compromised and including a password or the last four digits of a credit card number as evidence, but the yield from such scams seems to be low.
As I write, crime gangs have been making ever more use of spear-phishing in targeted attacks on companies where they install ransomware, steal gift coupons and launch other scams. In 2020, a group of young men hacked Twitter, where over a thousand employees had access to internal tools that enabled them to take control of user accounts; the gang sent bitcoin scam tweets from the accounts of such well-known users as Bill Gates, Barack Obama and Elon Musk [1294]. They appear to have honed their spear-phishing skills on SIM swap fraud, which I'll discuss later in sections 3.4.1 and 12.7.4. The spread of such ‘transferable skills’ among crooks is similar in many ways to the adoption of mainstream technology.
3.3.4 Opsec
Getting your staff to resist attempts by outsiders to inveigle them into revealing secrets, whether over the phone or online, is known in military circles as operational security or opsec. Protecting really valuable secrets, such as unpublished financial data, not-yet-patented industrial research and military plans, depends on limiting the number of people with access, and also on doctrines about what may be discussed with whom and how. It's not enough for rules to exist; you have to train the staff who have access, explain the reasons behind the rules, and embed them socially in the organisation. In our medical privacy case, we educated health service staff about pretext calls and set up a strict callback policy: they would not discuss medical records on the phone unless they had called a number they had got from the health service internal phone book rather than from a caller. Once the staff have detected and defeated a few false-pretext calls, they talk about it and the message gets embedded in the way everybody works.
Another example comes from a large Silicon Valley service firm, which suffered intrusion attempts when outsiders tailgated staff into buildings on campus. Stopping this with airport-style ID checks, or even card-activated turnstiles, would have changed the ambience and clashed with the culture. The solution was to create and embed a social rule that when someone holds open a building door for you, you show them your badge. The critical factor, as with the bogus phone calls, is social embedding rather than just training. Often the hardest people to educate are the most senior; in my own experience in banking, the people you couldn't train were those who were paid more than you, such as traders in the dealing rooms. The service firm in question did better, as its CEO repeatedly stressed the need to stop tailgating at all-hands meetings.
Some opsec measures are common sense, such as not throwing sensitive papers in the trash, or leaving them on desks overnight. (One bank at which I worked had the cleaners move all such papers to the departmental manager's desk.) Less obvious is the need to train the people you trust. A leak of embarrassing emails that appeared to come from the office of UK Prime Minister Tony Blair and was initially blamed on ‘hackers’ turned out to have been fished out of the trash at his personal pollster's home by a private detective [1210].
People operate systems however they have to, and this usually means breaking some of the rules in order to get their work done. Research shows that company staff have only so much compliance budget, that is, they're only prepared to put so many hours a year into tasks that are not obviously helping them achieve their goals [197]. You need to figure out what this budget is, and use it wisely. If there's some information you don't want your staff to be tricked into disclosing, it's safer to design systems so that they just can't disclose it, or at least so that disclosures involve talking to other staff members or jumping through other hoops.
But what about a firm's customers? There is a lot of scope for phishermen to simply order bank customers to reveal their security data, and this happens at scale, against both retail and business customers. There are also the many small scams that customers try on when they find vulnerabilities in your business processes. I'll discuss both types of fraud further in the chapter on banking and bookkeeping.
3.3.5 Deception research
Finally, a word on deception research. Since 9/11, huge amounts of money have been spent by governments trying to find better lie detectors, and deception researchers are funded across about five different subdisciplines of psychology. The polygraph measures stress via heart rate and skin conductance; it has been around since the 1920s and is used by some US states in criminal