Entries Tagged "computer security"

Page 15 of 33

Is Antivirus Dead?

This essay previously appeared in Information Security Magazine, as the second half of a point-counterpoint with Marcus Ranum. You can read his half here as well.

Security is never black and white. If someone asks, “for best security, should I do A or B?” the answer almost invariably is both. But security is always a trade-off. Often it’s impossible to do both A and B—there’s no time to do both, it’s too expensive to do both, or whatever—and you have to choose. In that case, you look at A and B and you make you best choice. But it’s almost always more secure to do both.

Yes, antivirus programs have been getting less effective as new viruses are more frequent and existing viruses mutate faster. Yes, antivirus companies are forever playing catch-up, trying to create signatures for new viruses. Yes, signature-based antivirus software won’t protect you when a virus is new, before the signature is added to the detection program. Antivirus is by no means a panacea.

On the other hand, an antivirus program with up-to-date signatures will protect you from a lot of threats. It’ll protect you against viruses, against spyware, against Trojans—against all sorts of malware. It’ll run in the background, automatically, and you won’t notice any performance degradation at all. And—here’s the best part—it can be free. AVG won’t cost you a penny. To me, this is an easy trade-off, certainly for the average computer user who clicks on attachments he probably shouldn’t click on, downloads things he probably shouldn’t download, and doesn’t understand the finer workings of Windows Personal Firewall.

Certainly security would be improved if people used whitelisting programs such as Bit9 Parity and Savant Protection—and I personally recommend Malwarebytes’ Anti-Malware—but a lot of users are going to have trouble with this. The average user will probably just swat away the “you’re trying to run a program not on your whitelist” warning message or—even worse—wonder why his computer is broken when he tries to run a new piece of software. The average corporate IT department doesn’t have a good idea of what software is running on all the computers within the corporation, and doesn’t want the administrative overhead of managing all the change requests. And whitelists aren’t a panacea, either: they don’t defend against malware that attaches itself to data files (think Word macro viruses), for example.

One of the newest trends in IT is consumerization, and if you don’t already know about it, you soon will. It’s the idea that new technologies, the cool stuff people want, will become available for the consumer market before they become available for the business market. What it means to business is that people—employees, customers, partners—will access business networks from wherever they happen to be, with whatever hardware and software they have. Maybe it’ll be the computer you gave them when you hired them. Maybe it’ll be their home computer, the one their kids use. Maybe it’ll be their cell phone or PDA, or a computer in a hotel’s business center. Your business will have no way to know what they’re using, and—more importantly—you’ll have no control.

In this kind of environment, computers are going to connect to each other without a whole lot of trust between them. Untrusted computers are going to connect to untrusted networks. Trusted computers are going to connect to untrusted networks. The whole idea of “safe computing” is going to take on a whole new meaning—every man for himself. A corporate network is going to need a simple, dumb, signature-based antivirus product at the gateway of its network. And a user is going to need a similar program to protect his computer.

Bottom line: antivirus software is neither necessary nor sufficient for security, but it’s still a good idea. It’s not a panacea that magically makes you safe, nor is it is obsolete in the face of current threats. As countermeasures go, it’s cheap, it’s easy, and it’s effective. I haven’t dumped my antivirus program, and I have no intention of doing so anytime soon.

Posted on November 10, 2009 at 6:31 AM • View Comments

"Evil Maid" Attacks on Encrypted Hard Drives

Earlier this month, Joanna Rutkowska implemented the “evil maid” attack against TrueCrypt. The same kind of attack should work against any whole-disk encryption, including PGP Disk and BitLocker. Basically, the attack works like this:

Step 1: Attacker gains access to your shut-down computer and boots it from a separate volume. The attacker writes a hacked bootloader onto your system, then shuts it down.

Step 2: You boot your computer using the attacker’s hacked bootloader, entering your encryption key. Once the disk is unlocked, the hacked bootloader does its mischief. It might install malware to capture the key and send it over the Internet somewhere, or store it in some location on the disk to be retrieved later, or whatever.

You can see why it’s called the “evil maid” attack; a likely scenario is that you leave your encrypted computer in your hotel room when you go out to dinner, and the maid sneaks in and installs the hacked bootloader. The same maid could even sneak back the next night and erase any traces of her actions.

This attack exploits the same basic vulnerability as the “Cold Boot” attack from last year, and the “Stoned Boot” attack from earlier this year, and there’s no real defense to this sort of thing. As soon as you give up physical control of your computer, all bets are off.

Similar hardware-based attacks were among the main reasons why Symantec’s CTO Mark Bregman was recently advised by “three-letter agencies in the US Government” to use separate laptop and mobile device when traveling to China, citing potential hardware-based compromise.

PGP sums it up in their blog.

No security product on the market today can protect you if the underlying computer has been compromised by malware with root level administrative privileges. That said, there exists well-understood common sense defenses against “Cold Boot,” “Stoned Boot” “Evil Maid,” and many other attacks yet to be named and publicized.

The defenses are basically two-factor authentication: a token you don’t leave in your hotel room for the maid to find and use. The maid could still corrupt the machine, but it’s more work than just storing the password for later use. Putting your data on a thumb drive and taking it with you doesn’t work; when you return you’re plugging your thumb into a corrupted machine.

The real defense here is trusted boot, something Trusted Computing is supposed to enable. But Trusted Computing has its own problems, which is why we haven’t seen anything out of Microsoft in the seven-plus years they have been working on it (I wrote this in 2002 about what they then called Palladium).

In the meantime, people who encrypt their hard drives, or partitions on their hard drives, have to realize that the encryption gives them less protection than they probably believe. It protects against someone confiscating or stealing their computer and then trying to get at the data. It does not protect against an attacker who has access to your computer over a period of time during which you use it, too.

EDITED TO ADD (10/23): A few readers have pointed out that BitLocker, the one thing that has come out of Microsoft’s Trusted Computing initiative in the seven-plus years they’ve been working on it, can prevent these sorts of attacks if the computer has a TPM module, version 1.2 or later, on the motherboard. (Note: Not all computers do.) I actually knew that; I just didn’t remember it.

EDITED TO ADD (11/12): Peter Kleissner’s Stoned Boot attacks on TrueCrypt.

EDITED TO ADD (12/9): A similar attack is possible against BitLocker with a TPM.

Posted on October 23, 2009 at 6:43 AM • View Comments

Ballmer Blames the Failure of Windows Vista on Security

According to the Telegraph:

Mr Ballmer said: “We got some uneven reception when [Vista] first launched in large part because we made some design decisions to improve security at the expense of compatibility. I don’t think from a word-of-mouth perspective we ever recovered from that.”

Commentary:

Vista’s failure and Ballmer’s faulting security is a bit of being careful for what you wish. Vista (codename “Longhorn” during its development) was always intended to be a more secure operating system. Following the security disasters and 2000 and 2001 that befell Windows 98 and 2000, Microsoft shut down all software development and launched the Trustworthy Computing Initiative that advocated secure coding practices. Microsoft retrained thousands of programmers to eliminate common security problems such as buffer overflows. The immediate result was a retooling of Windows XP to make it more secure for its 2002 launch. Long-term, though, was to make Vista the most secure operating system in Microsoft’s history.

What made XP and Vista more secure? Eliminating (or reducing) buffer overflow errors helped. But what really made a difference is shutting off services by default. Many of the vulnerabilities exploited in Windows 98, NT and 2000 were actually a result of unused services that were active by default. Microsoft’s own vulnerability tracking shows that Vista has far less reported vulnerabilities than any of its predecessors. Unfortunately, a Vista locked down out of the box made it less palatable to users.

Now security obstacles aren’t the only ills that Vista suffered. Huge memory footprint, incompatible graphics requirements, slow responsiveness and a general sense that it was already behind competing Mac and Linux OSes in functionality and features made Vista thud. In my humble opinion, the security gains in Vista were worth many of the tradeoffs; and it was the other technical requirements and incompatible applications that doomed this operating system.

There was also the problem of Vista’s endless security warnings. The problem is that they were almost always false alarms, and there were no adverse effects of ignoring them. So users did, which means they ended up being nothing but an annoyance.

Security warnings are often a way for the developer to avoid making a decision. “We don’t know what to do here, so we’ll put up a warning and ask the user.” But unless the users have the information and the expertise to make the decision, they’re not going to be able to. We need user interfaces that only put up warnings when it matters.

I never upgraded to Vista. I’m hoping Windows 7 is worth upgrading to. We’ll see.

EDITED TO ADD (10/22): Another opinion.

Posted on October 21, 2009 at 7:46 AM • View Comments

UK Defense Security Manual Leaked

Wow. It’s over 2,000 pages, so it’ll take time to make any sense of. According to Ross Anderson, who’s given it a quick look over, “it seems to be the bureaucratic equivalent of spaghetti code: a hodgepodge of things written by people from different backgrounds, and with different degrees of clue, in different decades.”

The computer security stuff starts at page 1,531.

EDITED TO ADD (10/6): An article.

Posted on October 5, 2009 at 3:10 PM • View Comments

Proving a Computer Program's Correctness

This is interesting:

Professor Gernot Heiser, the John Lions Chair in Computer Science in the School of Computer Science and Engineering and a senior principal researcher with NICTA, said for the first time a team had been able to prove with mathematical rigour that an operating-system kernel—the code at the heart of any computer or microprocessor—was 100 per cent bug-free and therefore immune to crashes and failures.

Don’t expect this to be practical any time soon:

Verifying the kernel—known as the seL4 microkernel—involved mathematically proving the correctness of about 7,500 lines of computer code in an project taking an average of six people more than five years.

That’s 250 lines of code verified per man-year. Both Linux and Windows have something like 50 million lines of code; verifying that would take 200,000 man-years, assuming no increased complexity resulting from the increased complexity. Clearly some efficiency improvements are required.

Posted on October 2, 2009 at 7:01 AM • View Comments

Subpoenas as a Security Threat

Blog post from Ed Felten:

Usually when the threat model mentions subpoenas, the bigger threats in reality come from malicious intruders or insiders. The biggest risk in storing my documents on CloudCorp’s servers is probably that somebody working at CloudCorp, or a contractor hired by them, will mess up or misbehave.

So why talk about subpoenas rather than intruders or insiders? Perhaps this kind of talk is more diplomatic than the alternative. If I’m talking about the risks of Gmail, I might prefer not to point out that my friends at Google could hire someone who is less than diligent, or less than honest. If I talk about subpoenas as the threat, nobody in the room is offended, and the security measures I recommend might still be useful against intruders and insiders. It’s more polite to talk about data losses that are compelled by a mysterious, powerful Other—in this case an Anonymous Lawyer.

Politeness aside, overemphasizing subpoena threats can be harmful in at least two ways. First, we can easily forget that enforcement of subpoenas is often, though not always, in society’s interest. Our legal system works better when fact-finders have access to a broader range of truthful evidence. That’s why we have subpoenas in the first place. Not all subpoenas are good—and in some places with corrupt or evil legal systems, subpoenas deserve no legitimacy at all—but we mustn’t lose sight of society’s desire to balance the very real cost imposed on the subpoena’s target and affected third parties, against the usefulness of the resulting evidence in administering justice.

The second harm is to security. To the extent that we focus on the subpoena threat, rather than the larger threats of intruders and insiders, we risk finding “solutions” that fail to solve our biggest problems. We might get lucky and end up with a solution that happens to address the bigger threats too. We might even design a solution for the bigger threats, and simply use subpoenas as a rhetorical device in explaining our solution—though it seems risky to mislead our audience about our motivations. If our solution flows from our threat model, as it should, then we need to be very careful to get our threat model right.

Posted on September 4, 2009 at 6:18 AM • View Comments

The Exaggerated Fears of Cyber-War

Good article, which basically says our policies are based more on fear than on reality.

On cyber-terrorism:

So why is there so much concern about “cyber-terrorism”? Answering a question with a question: who frames the debate? Much of the data are gathered by ultra-secretive government agencies—which need to justify their own existence—and cyber-security companies—which derive commercial benefits from popular anxiety. Journalists do not help. Gloomy scenarios and speculations about cyber-Armaggedon draw attention, even if they are relatively short on facts.

Politicians, too, deserve some blame, as they are usually quick to draw parallels between cyber-terrorism and conventional terrorism—often for geopolitical convenience—while glossing over the vast differences that make military metaphors inappropriate. In particular, cyber-terrorism is anonymous, decentralized, and even more detached than ordinary terrorism from physical locations. Cyber-terrorists do not need to hide in caves or failed states; “cyber-squads” typically reside in multiple geographic locations, which tend to be urban and well-connected to the global communications grid. Some might still argue that state sponsorship (or mere toleration) of cyber-terrorism could be treated as casus belli, but we are yet to see a significant instance of cyber-terrorists colluding with governments. All of this makes talk of large-scale retaliation impractical, if not irresponsible, but also understandable if one is trying to attract attention.

Much of the cyber-security problem, then, seems to be exaggerated: the economy is not about to be brought down, data and networks can be secured, and terrorists do not have the upper hand.

On cyber-war:

Putting these complexities aside and focusing just on states, it is important to bear in mind that the cyber-attacks on Estonia and especially Georgia did little damage, particularly when compared to the physical destruction caused by angry mobs in the former and troops in the latter. One argument about the Georgian case is that cyber-attacks played a strategic role by thwarting Georgia’s ability to communicate with the rest of the world and present its case to the international community. This argument both overestimates the Georgian government’s reliance on the Internet and underestimates how much international PR—particularly during wartime—is done by lobbyists and publicity firms based in Washington, Brussels, and London. There is, probably, an argument to be made about the vast psychological effects of cyber-attacks—particularly those that disrupt ordinary economic life. But there is a line between causing inconvenience and causing human suffering, and cyber-attacks have not crossed it yet.

The real risk isn’t cyber-war or cyber-terrorism, it’s cyber-crime.

Posted on September 2, 2009 at 7:40 AM • View Comments

Security vs. Usability

Good essay: “When Security Gets in the Way.”

The numerous incidents of defeating security measures prompts my cynical slogan: The more secure you make something, the less secure it becomes. Why? Because when security gets in the way, sensible, well-meaning, dedicated people develop hacks and workarounds that defeat the security. Hence the prevalence of doors propped open by bricks and wastebaskets, of passwords pasted on the fronts of monitors or hidden under the keyboard or in the drawer, of home keys hidden under the mat or above the doorframe or under fake rocks that can be purchased for this purpose.

We are being sent a mixed message: on the one hand, we are continually forced to use arbitrary security procedures. On the other hand, even the professionals ignore many of them. How is the ordinary person to know which ones matter and which don’t? The confusion has unexpected negative side-effects. I once discovered a computer system that was missing essential security patches. When I queried the computer’s user, I discovered that the continual warning against clicking on links or agreeing to requests from pop-up windows had been too effective. This user was so frightened of unwittingly agreeing to install all those nasty things from “out there” that all requests were denied, even the ones for essential security patches. On reflection, this is sensible behavior: It is very difficult to distinguish the legitimate from the illegitimate. Even experts slip up, as the confessions reported occasionally in various computer digests I attest.

Posted on August 5, 2009 at 6:10 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.