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:
F-Secure Labs reported this week on a new WhatsApp scam that’s successfully spammed over 22,000 people. Spam seems to be as old as the Internet itself, and is both a proven nuisance AND a lucrative source of revenue for spammers. Most people don’t see what goes on behind the scenes, but spammers often employ very sophisticated schemes that can expose web surfers to more than just ads for Viagara or other “magic beans”. Spam typically tries to drive Internet traffic by tricking people into clicking certain websites, where scammers can bombard unsuspecting web surfers with various types of advertising. Profit motives are what keep spammers working hard to circumvent spam blocks, white lists, and other protective measures that people use to try and fight back – and it can pay off. Numerous spammers have been indicted and suspected of generating hundreds of thousands of dollars in revenue from their spam campaigns, with one study projecting that spammers could generate in excess of 3.5 million dollars annually. While most spam circulates via e-mail, the popularity of services like WhatsApp is giving spammers new resources to exploit people, and new ways to make money. Here’s a few ways spammers and cyber criminals are using WhatsApp to make money off users: Following Malicious Links: One way that cyber criminals use WhatsApp to scam people is to trick them into following malicious links. For example, a recent scam sent SMS messages to WhatsApp users telling them to follow a link to update the app. But the message was not from WhatsApp, and the link didn’t provide them with any kind of update. It signed them up for an additional service, and added a hefty surcharge to victims' phone bills. Sending Premium Rate Messages: Premium rate SMS sending malware was recently determined by F-Secure Labs to be the fastest growing mobile malware threat, and WhatsApp gives cyber criminals a new way to engage in this malicious behavior. Basically the users receive a message that asks them to send a response – “I’m writing to you from WhatsApp, let me know here if you are getting my messages”, “Get in touch with me about the second job interview”, and various sexual themed messages have all been documented. Responding to these messages automatically redirects your message through a premium rate service. Spanish police claim that one gang they arrested made over 5 million euros using this scheme – leaving everyday mobile phone users to foot the bill. Manipulating Web Traffic: A lot of spam tries to direct web traffic to make money off advertising. As you might imagine, this means they have to get massive numbers of people to look at the ads they’re using for their scams. Scammers use WhatsApp to do this by using the app to spread malware or social engineer large numbers of people to visit a website under false pretenses. F-Secure Labs found that people were being directed to a website for information on where they could get a free tablet. In March there was a global spam campaign claiming people could test the new WhatsApp calling feature. Both cases were textbook scams, and instead of getting new tablets or services, the victims simply wasted their time spreading misleading spam messages and/or exposing themselves to ads. WhatsApp and other services are great for people, but like any new software, requires a bit of understanding to know how to use. Hopefully these points give WhatsApp users a heads up on how they can avoid spam and other digital threats, so they can enjoy using WhatsApp to chat with their friends. [ Image by Julian S. | Flickr ]
Espionage – it’s not just for James Bond type spies anymore. Cyber espionage is becoming an increasingly important part of global affairs, and a threat that companies and organizations handling large amounts of sensitive data are now faced with. Institutions like these are tempting targets because of the data they work with, and so attacks designed to steal data or manipulate them can give attackers significant advantages in various social, political and industrial theaters. F-Secure Labs’ latest malware analysis focuses on CozyDuke – an Advanced Persistent Threat (APT) toolkit that uses combinations of tactics and malware to compromise and steal information from its targets. The analysis links it to other APTs responsible for a number of high-profile acts of espionage, including attacks against NATO and a number of European government agencies. CozyDuke utilizes much of the same infrastructure as the platforms used in these attacks, effectively linking these different campaigns to the same technology. “All of these threats are related to one another and share resources, but they’re built a little bit differently to make them more effective against particular targets”, says F-Secure Security Advisor Sean Sullivan. “The interesting thing about CozyDuke is that it’s being used against a more diverse range of targets. Many of its targets are still Western governments and institutions, but we’re also seeing it being used against targets based in Asia, which is a notable observation to make”. CozyDuke and its associates are believed to originate from Russia. The attackers establish a beachhead in an organization by tricking employees into doing something such as clicking a link in an e-mail that distracts users with a decoy file (like a PDF or a video), allowing CozyDuke to infect systems without being noticed. Attackers can then perform a variety of tasks by using different payloads compatible with CozyDuke, and this can let them gather passwords and other sensitive information, remotely execute commands, or intercept confidential communications. Just because threats like CozyDuke target organizations rather than individual citizens doesn’t mean that they don’t put regular people at risk. Government organizations, for example, handle large amounts of data about regular people. Attackers can use CozyDuke and other types of malware to steal data from these organizations, and then use what they learn about people for future attacks, or even sell it to cyber criminals. The white paper, penned by F-Secure Threat Intelligence Analyst Artturi Lehtiö, is free and available for download from F-Secure’s website. [ Image by Andrew Becraft | Flickr ]
Malware is an omniscient threat – it’s present even when people don’t realize it. Understanding the threat is a key component of protecting yourself and your devices, and nothing drives that point home like cold hard facts and comprehensive research. F-Secure just released its latest Threat Report, which provides important insights into contemporary digital threats. The report details the various changes and trends in the digital threat landscape using data collected during the 2nd half of 2014. The threat report is full of important information, and it’s worth checking out to get some ideas about what attackers are cooking up. Trends like social media malware, exploits, and ransomware are detailed in the report. But there’s tons of important information people should be aware of, and so we put together an infographic to give you a quick overview of the report. The report provides lots more information about the threats, incidents, and trends that were prominent in the latter half of 2014. There's also some insightful words penned by F-Secure security researchers to give you a little context about why you need to arm yourself with knowledge to defend yourself against digital threats. You can download the full threat report for free from F-Secure’s website.