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Botnets: Is size everything?

The botnets behind DDoS attacks have transformed the attack landscape as we know it, writes Dave Larson, pictured, COO at Corero Network Security.

They use vast size and power, as well as being deployed in ever more complex ways to further confuse those tasked with defending against them. It is also increasingly difficult to pinpoint those behind the botnets and put a stop to their activities. So how can organisations successfully defend against these attacks, both now and in the future? Once, attacks were the preserve of a small, technical elite who had enough coding skills to launch a strike. But now, DDoS-for-hire botnets have significantly lowered the barriers to entry. A quick Google search and a PayPal account makes botnets readily available for just a few dozen dollars, with no coding experience necessary. And they are becoming increasingly popular – DDoS-for-hire botnets are now estimated to be behind as many as 40 per cent of all network layer attacks.

But while the majority of purchasers are likely to be low-level attackers, seeking to cause mischief and settle personal grievances, more powerful botnets-for-hire are also being utilised by state actors and organised crime syndicates. In recent years, DDoS attacks have been getting bigger and bigger. Our Security Operations Centre recorded a dramatic (25%) increase in very large attacks of more than 10Gb per second among our customer base in the second half of last year. And in terms of individual attacks, the strike on the BBC in January was one of the biggest ever reported, at an enormous 600Gb per second. While these attacks clearly cause significant damage, we believe that their primary purpose is often just to demonstrate their attackers’ capabilities so that they can be sold as a service in the future. The kind of gigantic attacks that make headlines aren’t cheap to rent, and would probably cost upwards of $150,000 to engage. As a result, these are only likely to be utilised by criminal or nation state attackers, who have access to a sophisticated infrastructure with money laundering capabilities. Looking forward, there is really no limit to the potential size and scale of future botnet-driven DDoS attacks, particularly when they harness the full range of smart devices incorporated into our Internet of Things. By using amplification techniques on the millions of very high bandwidth density devices currently accessible, such as baby video monitors and security cameras, DDoS attacks are set to become even more colossal in scale. Terabit -class attacks may be increasingly common and ‘breaking the Internet’ – or at least clogging it in certain regions – could soon become a reality. The bottom line is that attacks of this size can take virtually any company offline, and are a reality that anyone with an online presence must be prepared to defend against.

But it isn’t just the giant attacks that organisations need to worry about. Before botnets are mobilised, hackers need to make sure that their techniques are going to work. This is usually done through the use of small, sub-saturating attacks which most IT teams wouldn’t even recognise as a DDoS attack. Due to their size – the majority are less than five minutes in duration and under 1Gbps – these shorter attacks typically evade detection by most legacy out-of-band DDoS mitigation tools, which are generally configured with detection thresholds that ignore this level of activity. This allows hackers to perfect their methods under the radar, leaving security teams blindsided by subsequent attacks. If these techniques are then deployed at full scale with a botnet, the results can be devastating.

Besides harnessing enormous power, botnets are also notoriously difficult to spot. Once deployed, they utilise sophisticated techniques to hide their tracks. Their command and control infrastructure can be automated or set on autopilot, they can sleep for long periods of time, they can have ubiquitous bandwidth available at any time of day by waking up different regions at different times – they are a complex and vast maze, often operated by some of the brightest minds in cybercrime. But that’s no reason for organisations to resign themselves to eventually getting attacked. So what are the most effective methods of defence?

Effective DDoS defence that’ll stand up to the test will have to tick three main boxes – it has to be always-on, respond automatically and be deployed in-line – meaning humans are out the window. With these boxes ticked, traffic is constantly monitored and the attack traffic can be removed in real-time, while the humans on the security team can watch for data exfiltration and other criminal activities that come with a powerful cyber attack.
Modern botnet-driven DDoS attacks warrant a contemporary response, rather than legacy solutions. Due to the fact that botnet attacks are launched and then disappear without leaving enough information for victims to trace its origins – effectively acting like a giant cloud computer – organisations really have no choice but to defend themselves at the edges of the network. Out-of-band scrubbing solutions which require human intervention and reactive countermeasures to remove the attack will not be successful, and using such systems will also allow hackers to experiment on your networks undetected, finding vulnerabilities and testing new methods through smaller, hidden attacks. Automated, in-line DDoS systems come in various forms, whether as a service from an upstream provider or bought by the organisation itself and deployed on-premises. Either way, blocking all attacks in-line and preventing downtime is the only robust defence against today’s botnet-driven DDoS attacks.


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