Active Defense and "Hacking Back": A Primer
In the lead piece in this package, Idaho National Lab’s Andy Bochman puts forth a provocative idea: that no amount of spending on technology defenses can secure your critical systems or help you keep pace with hackers. To protect your most valuable information, he argues, you need to move beyond so-called cyber hygiene, the necessary but insufficient deployment of security software and network-monitoring processes.
Bochman lays out a framework that requires switching your focus from the benefits of efficiency to the costs. Ideas that were once anathema — unplug some systems from the internet, de-automate in some places, insert trusted humans back into the process — are now the smart play.
But they’re not the only play. Another that’s gaining attention is “active defense.” That might sound like Orwellian doublespeak, but it’s a real strategy. It involves going beyond passive monitoring and taking proactive measures to deal with the constant attacks on your network.
There’s just one problem: As active defense tactics gain popularity, the term’s definition and tenets have become a muddy mess. Most notably, active defense has been conflated with “hacking back” — attacking your attackers. The approaches are not synonymous; there are important differences with respect to ethics, legality, and effectiveness.
Active defense has a place in every company’s critical infrastructure-protection scheme. But to effectively deploy it, you need a proper understanding of what it is — and that’s tougher to come by than you might expect.
We enlisted two of the foremost experts on the topic to help us proffer an authoritative definition of active defense and give you a fundamental understanding of how to deploy it.
Dorothy Denning was an inaugural inductee into the National Cyber Security Hall of Fame. A fellow of the Association for Computing Machinery and a professor at the Naval Postgraduate School, she has written several books on cybersecurity, including Information Warfare and Security. She also coauthored a landmark paper on active defense, which states, “When properly understood, [active defense] is neither offensive nor necessarily dangerous.”
Robert M. Lee is a cofounder of Dragos, an industrial security firm. He conducted cyber operations for the NSA and U.S. Cyber Command from 2011 to 2015. In October 2017 his firm identified the first known malware written specifically to target industrial safety systems — in other words, its sole purpose was to damage or destroy systems meant to protect people. (The malware had been deployed that August against a petrochemical plant in Saudi Arabia, but the attack failed.) When asked about active defense, Lee sighs and asks flatly, “How are you defining it?” You can tell he’s had this conversation before. The number of people co-opting the term seems to have wearied him, and he’s happy to help bring clarity to the idea.
The following FAQ primer draws on interviews with Denning and Lee.
What exactly is active defense, also known as active cyber defense?
It depends on whom you ask. The term has almost as many definitions as it does citations. NATO defines active defense this way: “A proactive measure for detecting or obtaining information as to a cyber intrusion, cyber attack, or impending cyber operation or for determining the origin of an operation that involves launching a preemptive, preventive, or cyber counter-operation against the source.”
A solid working definition can be found in Denning’s paper with Bradley J. Strawser, “Active Cyber Defense: Applying Air Defense to the Cyber Domain”: Active cyber defense is a direct defensive action taken to destroy, nullify, or reduce the effectiveness of cyber threats against friendly forces and assets.
That sounds like offense, but Lee and Denning note that it describes a strictly defensive action — one taken in reaction to a detected infiltration. Lee argues that there’s a border distinction: Active defense happens when someone crosses into your space, be it over a political boundary or a network boundary. But Denning says that’s probably too simple, and below we’ll see a case in which the line is blurred. Lee says, “Most experts understand this, but it’s important to point out, especially for a general audience. You are prepared to actively deal with malicious actors who have crossed into your space. Sending missiles into someone else’s space is offense. Monitoring for missiles coming at you is passive defense. Shooting them down when they cross into your airspace is active defense.”
Can you give some other examples?
Denning says, “One example of active cyber defense is a system that monitors for intrusions, detects one, and responds by blocking further network connections from the source and alerting the system administrator. Another example is taking steps to identify and shut down a botnet used to conduct distributed denial-of-service (DDoS) attacks.” It’s the verbs “responds” and “shut down” that make these instances of active defense. An example of passive defense, in contrast, is an encryption system that renders communications or stored data useless to spies and thieves.
Is active defense only an information security concept?
Not at all. Some argue that it dates back to The Art of War, in which Sun Tzu wrote, “Security against defeat implies defensive tactics; ability to defeat the enemy means taking the offensive.” Centuries later Mao Zedong said, “The only real defense is active defense,” equating it to the destruction of an enemy’s ability to attack — much as aggressive tactics in active cyber defense aim to do. The term was applied in the Cold War and, as Denning and Strawser’s paper makes clear, is a core concept in air missile defense. Tactics are tactics; all that changes is where they’re employed.
That seems pretty straightforward. So why the uncertainty around the definition?
As noted earlier, hacking back — also not a new term — has confused matters. Properly used, it refers to efforts to attack your attackers on their turf. But because people often fuse it with active defense, difficult and sometimes frustrating disputes over the merits of active defense have ensued. One research paper went so far as to equate the two terms, starting its definition, “Hack back — sometimes termed ‘active defense’…”
The confusion multiplied in October 2017, when Representatives Tom Graves (R-GA) and Kyrsten Sinema (D-AZ) introduced the Active Cyber Defense Certainty (ACDC) bill, which would allow companies to gain unauthorized access to computers in some situations in order to disrupt attacks. The lawmakers called this active defense. The media called it the “hack back bill.” What it would and would not allow became the subject of hot debate. The idea that companies could go into other people’s infected computers wasn’t welcomed. Some savaged the bill. The technology blog network Engadget called it “smarmy and conceited” and observed, “When you try to make laws about hacking based on a child’s concept of ‘getting someone back,’ you’re getting very far and away from making yourself secure. It’s like trying to make gang warfare productive.” The bill went through two iterations and is currently stalled.
But is hacking back part of active defense?
Probably not. Lee says unequivocally, “Hacking back is absolutely not active defense. It’s probably illegal, and it’s probably not effective. We don’t have evidence that attacking attackers works.” Denning has a somewhat different take. “Hacking back is just one form of active defense,” she says. “It might be used to gather intelligence about the source of an intrusion to determine attribution or what data might have been stolen. If the attacker is identified, law enforcement might bring charges. If stolen data is found on the intruder’s system, it might be deleted. Hacking back might also involve neutralizing or shutting down an attacking system so that it cannot cause further damage.”
But Lee and Denning are defining the term differently. And Denning’s version refers to actions undertaken with proper authority by government entities. When it comes to hacking back on the part of businesses, the two experts are in total agreement: Don’t do it. Denning says, “Companies should not hack back. The Department of Justice has advised victims of cyberattacks to refrain from any ‘attempt to access, damage, or impair another system that may appear to be involved in the intrusion or attack.’ The advice contends that ‘doing so is likely illegal, under U.S. and some foreign laws, and could result in civil and/or criminal liability.’”
What’s an example of an aggressive form of active defense that some might consider hacking back?
Denning says, “One of my favorite examples of active defense led to the exposure of a Russian hacker who had gotten malicious code onto government computers in the country of Georgia. The malware searched for documents using keywords such as “USA” and “NATO,” which it then uploaded to a drop server used by the hacker. The Georgian government responded by planting spyware in a file named “Georgian-NATO Agreement” on one of its compromised machines. The hacker’s malware dutifully found and uploaded the file to the drop server, which the hacker then downloaded to his own machine. The spyware turned on the hacker’s webcam and sent incriminating files along with a snapshot of his face back to the Georgian government.
Is that hacking back? I don’t think so. It was really through the hacker’s own code and actions that he ended up with spyware on his computer.”
Note that the actions were taken by a government and occurred within its “borders”; Georgia put the spyware on its own computer. It did not traverse a network to hit another system. It was the hacker’s action of illegally taking the file that triggered the surveillance.
If it’s probably illegal and ineffective, why is hacking back getting so much press?
Companies are weary. “They are under constant attack and working so hard and spending so much just to keep up, and they can’t keep up,” Lee says. “This is a moment when we’re looking for new ideas. That’s why Bochman’s concept of unplugging systems and not always going right to the most efficient solution is starting to be heard. Hacking back feels like another way to turn the tide. Cybersecurity loves a silver bullet, and this feels like one. CEOs are probably thinking, ‘Nothing else has worked; let’s fight.’” Lee has heard many business leaders express these sentiments, especially if their companies have suffered damaging attacks. “This is an emotional issue,” he says. “You feel violated, and you want to do something about it.”
In a paper titled “Ethics of Hacking Back,” Cal Poly’s Patrick Lin captures the sense of utter vulnerability that could lead some to desire vigilante justice:
In cybersecurity, there’s a certain sense of helplessness — you are mostly on your own. You are often the first and last line of defense for your information and communications technologies; there is no equivalent of state-protected borders, neighborhood police patrols, and other public protections in cyberspace. For instance, if your computer were hit by “ransomware” — malware that locks up your system until you pay a fee to extortionists — law enforcement would likely be unable to help you. The U.S. Federal Bureau of Investigation (FBI) offers this guidance: “To be honest, we often advise people to just pay the ransom,” according to Joseph Bonavolonta, the Assistant Special Agent in Charge of the FBI’s CYBER and Counterintelligence Program. Do not expect a digital cavalry to come to your rescue in time. As online life moves at digital speeds, law enforcement and state responses are often too slow to protect, prosecute, or deter cyberattackers. To be sure, some prosecutions are happening but inconsistently and slowly. The major cases that make headlines are conspicuously unresolved, even if authorities confidently say they know who did them.
What are the ethics of hacking back?
For the most part, experts say that hacking back without legal authorization or government cooperation is unethical. And whenever activities leave your boundaries, it’s hard to condone them. The targets are too evasive, and the networks are too complex, traversing innocent systems and affecting the people working with them. In addition, Lee points out that government entities might be tracking and dealing with malicious actors, and hacking back could compromise their operations. “Leave it to the pros,” he says.
Denning stresses that unintended consequences are not just possible but likely. She says, “The biggest risks come when you start messing with someone else’s computers. Many cyberattacks are launched through intermediary machines that were previously compromised by the attacker. Those computers could be anywhere, even in a hospital or power plant. So you don’t want to shut them down or cause them to malfunction.”
What kind of work is under way with regard to ethics?
According to Denning, researchers began wrestling with these issues as early as 2006. Speaking about a workshop she participated in, she says, “I recall discussions about measures that involved tracing back through a series of compromised machines to find the origin of an attack. Such tracebacks would involve hacking into the compromised machines to get their logs if the owners were not willing or could not be trusted to help out.”
A decade later Denning collaborated with Strawser to examine the morality of active defense writ large, using the ethics of air defense and general war doctrine as a guide. They wrote that harm to “non-combatants” — especially and most obviously physical harm — disqualifies an active defense strategy. But they say that “temporary harm to the property of non-combatants” is sometimes morally permissible. (It should be noted Denning is primarily focused on the government use of active cyber defense strategies). Denning cites the takedown of Coreflood — malware that infected millions of computers and was used as a botnet. The Justice Department won approval to seize the botnet by taking over its command-and-control servers. Then, when the bots contacted the servers for instructions, the response was essentially, “Stop operating.” In the instance of Coreflood, as in some similar cases, a judge decided that the actions could proceed because they could shut down major malicious code without damaging the infected systems or accessing any information on them.
“The effect was simply to stop the bot code from running. No other functions were affected, and the infected computers continued to operate normally,” Denning says. “There was virtually no risk of causing any harm whatsoever, let alone serious harm.”
Still, the case may have set a precedent for at least the suggestion of more-aggressive measures, such as the ACDC bill. If the government can take control of command-and-control servers, it can, in theory, do more than just tell the bots to shut down. Why not grab some log files at the same time? Or turn on the webcam, as in the Georgian-NATO case? Oversight is needed in all active defense strategies.
How can I deploy an ethical and effective active defense strategy?
If you have or subscribe to services that can thwart DDoS attacks and create logs, you’ve already started. Denning says that many companies are doing more active defense than they realize. “They might not call it active defense, but what they call it matters less than what they do.”
Cooperating with law enforcement and the international network of companies and organizations combating hacking is also part of an active defense strategy. The more companies and agencies that work together, the more likely it is that active defense strategies like the one that took out Coreflood can be executed without harm. Several such operations have taken place without reports of problems.
Denning recommends A Data-Driven Computer Security Defense: THE Computer Security Defense You Should Be Using, by Roger A. Grimes. (Full disclosure: Denning wrote the foreword. “But the book really is good!” she says.)
As for more-aggressive tactics, like the ones proposed in the ACDC bill, proceed with caution. Work with law enforcement and other government agencies, and understand the risks. Denning says, “It’s all about risk. Companies need to understand the threats and vulnerabilities and how security incidents will impact their company, customers, and partners. Then they need to select cost-effective security defenses, both passive and active. “There are limits, she cautions. “Security is a bottomless pit; you can only do so much. But it’s important to do the right things — the things that will make a difference.”
Scott Berinato is a senior editor at Harvard Business Review and the author of “Good Charts: The HBR Guide to Making Smarter, More Persuasive Data Visualizations”.