Someone once made the comment, “Most people, I think, don’t even know what a rootkit is, so why should they care about it?”
That was in in 2005, when rootkits were an unknown menace for most users. Nowadays, that isn’t quite the case any more, as the number of rootkit infections have exploded in the last few years and lead to more media coverage. In any case, you know a malware has reached evil superstar status when it warrants its own ‘For Dummies’ book.
In the beginning (as in the late 1980s), rootkits were standalone toolkits that allowed hackers to gain root, or administrative access to a computer system (hence the name). Today, the term is usually used to mean programs, codes or techniques that are used to hide malware on an computer.
I’m not going to dwell much on their history or workings (though if you’re interested, Alisa Shevchenko over on Securelist has an excellent article on rootkit history). Instead, I’m going to focus on one particular aspect of rootkits that’s been irritating the daylights out of our Support and Analyst folks recently – why are they so difficult to remove?
Media reports tend to hype ‘rootkits’ as the next big evil in computing, but it’s a bit more complicated than that. For one thing, rootkit tools, coding or techniques aren’t strictly illegal, or even undesirable – perfectly legitimate commercial applications use them to the benefit of users. It also doesn’t help that security vendors don’t have a uniform approach to rootkits; some consider all rootkits as a type of malware, while others shade their evaluations depending on whether the rootkit-like behavior is in a commercial software (in which case, the program may just be potentially unwanted).
Personally, I find it more useful to think of rootkits as operating system controllers. Their entire purpose is to burrow deep into the operating system’s files and subroutines, latching onto and modifying specific processes to gain control over the system. The processes targeted will vary depending on the system and the rootkit in question, but the end result is the same – the rootkit is now in a position to direct the system’s actions for its own ends; it’s become the puppeteer to the computer’s marrionette.
Rootkits have been around a long time, but they only really became a major concern for most users when malware authors found ways to incorporate rootkits into their malicious programs. And for most security professionals, rootkits are considered one of the most troublesome threats to deal with.
A rootkit’s defining characteristic is that it has administrative access – its commands are accepted by the operating system as though they were its own. How this access is gained is another story – a separate trojan may exploit a vulnerability to gain access to a administrator account, or a worm might steal the necessary passwords, any number of things. However the access is gained, the end result is that the rootkit is installed with admin rights, and from there proceeds to do its dirty work.
Rootkits use their privileged access to control the operating system itself, mainly by intercepting and modifying the commands it sends to other programs and basic system activities. Slightly more technically, rootkits usually manipulate various application programming interfaces (APIs), or the subroutines used by the operating system to direct operations (at least, in Windows).
An important point to remember is that these APIs are a built-in features of the operating system. They may be undocumented, or rarely used – but commands made through them are perfectly legitimate, and recognized and treated as such. These APIs can involve and affect every activity performed on the computer, from the mundane (e.g., displaying a folder) to the most fundamental (e.g., booting up).
There are various types of rootkits based on how deeply they can penetrate the operating system to control its most basic processes (if you want to get more technical, Joanna Rutkowska has a good article), but in every case, the key idea is the same – commands sent by the operating system can be viewed and countermanded by the rootkit, if necessary; likewise, requests coming from other programs or system processes are checked and filtered by the rootkit before they reach the operating system.
To illustrate why a rootkit’s manipulation of APIs is significant, let’s compare it to other malwares. When a trojan or virus infects a computer, its interactions with the operating system will usually fall into one of two strategies:
Note that strategy 1 involves the malware functioning just like any other program – its processes and files are visible, the instructions between operating system and program are ‘standard’, and so on. Strategy 2 usually involves some novel technique that forces the system to behave in an unintended manner – ‘breaking the system’, if you like.
Rootkits on the other hand, doesn’t do either. Unlike trojans or viruses, the rootkit doesn’t behave like a separate program being run on top of the operating system; instead, the rootkit acts more like a driver, or one of the operating system’s own components, giving directions on how other programs should be handled. The rootkit also doesn’t exploit any vulnerabilities – it simply uses the operating system’s own features for its own ends.
The thing is, malwares that use Strategies 1 & 2 can be defeated with fairly standard countermeasures: for example, software vendors can release patches to close vulnerabilities, and users can uninstall malicious programs. Rootkits however don’t suffer either problem: there’s no vulnerability that can be patched, and because a rootkit’s first action is usually to hide itself, the rootkit can effectively prevent the user or the operating system from detecting its presence at all, let alone uninstalling it.
The highly technical reason for this is: you can’t remove a file you can’t find. Remember, the rootkit is in control. If the user starts looking through system folders for suspicious files, or starts an antivirus scan, a sophisticated rootkit can display a clean ‘image’ of the infected folder rather than the actual infected one, or move the infected file to another location for the duration of the scan; it can stop the antivirus from running, or force it to report false scan results; anything, really, to prevent detection.
Malware authors really want their creations stay installed and active on your computer, and they can use the rootkit to perform any number of actions to prevent their malwares – or the rootkit itself – from being detected. Some of the tricks they can use to get their way include:
Heck, about the only thing they don’t do is say they love you and will still respect you in the morning.
Antivirus programs have historically had a difficult time dealing with rootkits, precisely because of how they operate: by using the operating system itself to evade detection and prevent removal. In the case of simpler rootkits, it was possible to look for telltale signs – odd changes, missing or alter folders, etc, to determine a rootkit was present. With more sophisticated threats though, detection meant deactivating the rootkit entirely before it could start active evasion; because once it was active, detection and removal became well nigh impossible.
That status quo has changed somewhat in the last few years, as more antivirus vendors have developed the necessary tools to combat the threat. As rootkits themselves vary in complexity, detecting and removing them requires a multi-layered approach:
These detection and removal methods will probably catch most of the rootkits out there, but none of them are 100% certain. In some cases, the fastest, easiest and cheapest possible solution is to simply format and reinstall the entire operating system (assuming of course you have backups of your important files). Determining whether that applies in your case really depends on your personal evaluation of the costs and benefits though, so it’s hard to state any hard and fast rule about this.
Unfortunately, malware authors are ingenious at finding ways to get where they’re not wanted, and the highly complex, multi-layered nature of computing tilts the odds in their favour more than it does to ensuring computer security. Then again, to be fair, humans have lived in houses for thousands of years, and we still haven’t figured out how to totally prevent burglars from invading our homes, so you could probably also credit a natural human genius for finding ways to inconvenience their fellows.
If you’re still interested, here are few other articles with more details (some technical, others less so) about rootkits:
Also partially available in Google Books:
For this year's World Day against Cyber Censorship, F-Secure is giving away free subscriptions for our one-button Freedome app. You can use the key qsf257 to get a free 3-month subscription to Freedome! Freedom of expression is an important issue for everyone. Developments over the past year have highlighted how sensitive the matter is. It transcends national and cultural borders, yet these borders shape the issue differently for people across the globe. It belongs to us all, but it means different things to different people. Reporters without Borders launched the World Day against Cyber Censorship in 2008. Its intent is to raise awareness that our rights to say what we really think are not something to take for granted. Free speech is a dynamic concept that constantly grows and contracts in the face of developments that threaten its growth. While the Internet has given many people across the globe a powerful new voice, there are always threats mobilizing against this invaluable resource. The World Day against Cyber Censorship draws attention to this struggle. Last year Reporters without Borders compiled a list of what they call “Enemies of the Internet” as part of the annual event. If you look through it you’ll notice a diverse list of government agencies from nations across the world. Many of the events that highlight the fragility of our digital freedoms are attributable to these institutions, such as the Gemalto hack that saw the encryption keys to millions of phone calls stolen by the NSA and its fellow conspirators. And in some cases surveillance is just the beginning, as once these institutions identify their targets they can escalate their actions to include oppression. Hong Kong protestors saw this when local pro-democracy websites became infected with malware. Turkish people saw this during the Twitter crackdown. Drawing attention to these agencies as “enemies” of the Internet places the struggle within a larger dichotomy – enemies and allies. Even if it is a bit of a cliché or oversimplification of the conflict, it points out that people still have an opportunity to mobilize and assert their rights. And nobody is alone in this fight - we all have enemies and allies in this struggle. Having said all of this, World Day against Cyber Censorship isn't all about doom-and-gloom. Reporters without Borders is working to circumvent a number of websites blocked by governments. The Electronic Frontier Foundation continues to work to inform, educate, and represent the voices crying out for a free and open Internet. And F-Secure wants to help by making privacy and security solutions easy and accessible for people all over the world. Just get your trial version of the app and then use the key when it asks for your subscription number. Freedome gives you a one-button app that lets you encrypt your communications, disable trackers, and even change your virtual location. Check out this blog post for more information about the app. It's first come first serve, so don't miss this chance to take control of your digital freedom!
This year’s Mobile World Congress (MWC) is coming up next week. The annual Barcelona-based tech expo features the latest news in mobile technologies. One of the biggest issues of the past year has enticed our own digital freedom fighter Mikko Hypponen to participate in the event. Hypponen, a well-known advocate of digital freedom, has been defending the Internet and its users from digital threats for almost 25 years. He’s appearing at this year’s MWC on Monday, March 2 for a conference session called “Ensuring User-Centred Privacy in a Connected World”. The panel will discuss and debate different ways to ensure privacy doesn’t become a thing of the past. While Hypponen sees today’s technologies as having immeasurable benefits for us all, he’s become an outspoken critic of what he sees as what’s “going wrong in the online world”. He’s spoken prominently about a range of these issues in the past year, and been interviewed on topics as diverse as new malware and cybersecurity threats, mass surveillance and digital privacy, and the potential abuses of emerging technologies (such as the Internet of Things). The session will feature Hypponen and five other panelists. But, since the event is open to public discussion on Twitter under the #MWC15PRIV hashtag, you can contribute to the conversation. Here’s three talking points to help you get started: Security in a mobile world A recent story broken by The Intercept describes how the American and British governments hacked Gemalto, the largest SIM card manufacturer in the world. In doing so, they obtained the encryption keys that secure mobile phone calls across the globe. You can read a recent blog post about it here if you’re interested in more information about how this event might shape the discussion. Keeping safe online It recently came to light that an adware program called “Superfish” contains a security flaw that allows hackers to impersonate shopping, banking, or other websites. These “man-in-the-middle” attacks can be quite serious and trick people into sharing personal data with criminals. The incident highlights the importance of making sure people can trust their devices. And the fact that Superfish comes pre-installed on notebooks from the world’s largest PC manufacturer makes it worth discussing sooner rather than later. Privacy and the Internet of Things Samsung recently warned people to be aware when discussing personal information in front of their Smart TVs. You can get the details from this blog post, but basically the Smart TVs voice activation technology can apparently listen to what people are saying and even share the information with third parties. As more devices become “smart”, will we have to become smarter about what we say and do around them? The session is scheduled to run from 16:00 – 17:30 (CET), so don’t miss this chance to join the fight for digital freedom at the MWC. [Image by Hubert Burda Media | Flickr]
Ordinary people here in Finland have been confronted with yet another cybersecurity acronym lately, DoS. And this does not mean that retro-minded people are converting back to the pre-Windows operating system MS-DOS that we used in the eighties. Today DoS stands for Denial of Service. This case started on New Year’s Eve when customers of the OP-Pohjola bank experienced problems withdrawing cash from ATMs and accessing the on-line bank. The problems have now continued with varying severity for almost a week. What happens behind the scene is that someone is controlling a large number of computers. All these computers are instructed to bombard the target system with network traffic. This creates an overload situation that prevents ordinary customers from accessing the system. It’s like a massive cyber traffic jam. The involved computers are probably ordinary home computes infected with malware. Modern malware is versatile and can be used for varying purposes, like stealing your credit card number or participating in DoS-attacks like this. But what does this mean for me, the ordinary computer user? First, you are not at risk even if a system you use is the victim of a DoS-attack. The attack cannot harm your computer even if you try to access the system during the attack. Your data in the target system is usually safe too. The attack prevents people from accessing the system but the attackers don’t get access to data in the system. So inability to use the system is really the only harm for you. Well, that’s almost true. What if your computer is infected and participates in the attack? That would use your computer resources and slow down your Internet connection, not to speak about all the other dangers of having malware on your system. Keeping the device clean is a combination of common sense when surfing and opening attachments, and having a decent protection program installed. So you can participate in fighting DoS-attacks by caring for your own cyber security. But why? Who’s behind attacks like this and what’s the motive? Kids having fun and criminals extorting companies for money are probably the most common motives right now. Sometimes DoS-victims also accuse their competitors for the attack. But cases like this does always raise interesting questions about how vulnerable our cyber society is. There has been a lot of talk about cyber war. Cyber espionage is already reality, but cyber war is still sci-fi. This kind of DoS-attack does however give us a glimpse of what future cyber war might look like. We haven’t really seen any nations trying to knock out another county’s networks. But when it happens, it will probably look like this in greater scale. Computer-based services will be unavailable and even radio, TV, electricity and other critical services could be affected. So a short attack on a single bank is more like an annoyance for the customers. But a prolonged attack would already create sever problems, both for the target company and its customers. Not to talk about nation-wide attacks. Cyber war might be sci-fi today, but it is a future threat that need to be taken seriously. Safe surfing, Micke Image by Andreas Kaltenbrunner.