Eight years ago, on November 21st, 2008, Conficker reared its ugly head. And since then, the “worm that roared” – as ESET’s distinguished researcher Aryeh Goretsky puts it – has remained stubbornly active.

Targeting Microsoft Windows, it has compromised home, business and government computers across 190 countries, leading experts to call it the most notorious and widespread worm since the emergence of Welchia some five years earlier.

Conficker, as we’ll go onto explore, spawned numerous versions, each promising different attack methods (from injecting malicious code to phishing emails and copying itself to the ADMIN part of a Windows machine). Ultimately though, the worm leveraged – and indeed, continues to leverage – an old, unpatched vulnerability to crack passwords and hijack Windows computers into a botnet. These botnets would then be used to distribute spam or install scareware (again, as they are today).

11 million devices and counting

It became one of the most serious malware outbreaks of all time, and claimed some famous scalps.

Some 11 million devices are reported to have been infected to date, including machines at the UK’s Ministry of Defence and Germany’s unified armed forces, Bundeswehr.

Reportedly it cost one UK council £1.4 million to recover from a Conficker infection in 2009, while Quest France complained French fighter planes were grounded because of the worm.

Such notoriety caused the Department of Homeland Security in the US to fund The Conficker Working Group, containing members from ESET, CISCO, Facebook, ICANN, Microsoft and various others, in order to investigate its long-term impact.

According to analysts at the Cyber Secure Initiative, worldwide costs of the Conficker cleanup might have been as much as $9 billion. There were also concerns of a bigger impact on the internet’s infrastructure.

"With millions of computers under its control, many security experts speculated as to what the authors would attempt to do,” a paper from the working group stated.

"The worm, properly instructed, could credibly threaten critical infrastructure on the internet."

“The worst case scenarios were bleak. The worm, properly instructed, could credibly threaten critical infrastructure on the internet. Even the more benign uses could cause severe problems for the public or private sector."

This was still back in 2009 though, and more recently Conficker is said to have corrupted and hijacked emerging IoT devices, including connected MRI machines, CT scanners and dialysis pumps (as well as police body-worn cameras), stealing medical records on the former. It is, subsequently, seen as the most pervasive malware family ahead of other long-timers like Tinba and Sality.

In truth, part of Conficker’s success has been down to the numerous new variants and revised methods of attack. More recently, analysts have said that the self-replicating malware - once best known for infecting via USB - would be able to move laterally through a network in order to target certain devices, orchestrated by the criminal’s command and control (C&C) instructions.

Microsoft even offered a $250,000 reward in 2009 for anyone providing information that would lead to the “arrest and conviction” of anyone found guilty of “illegally launching the Conficker malicious code on the internet”. It’s a reward that has seemingly never been paid.

"People who write this malware have to be held accountable," George Stathakopulos, of Microsoft's Trustworthy Computing Group, said at the time.

And as we’ll go onto discuss, it seems like Conficker became too big a beast for any cybercriminal to truly make use of.

Attacks change over time

Conficker was notorious, and - perhaps unsurprisingly - its success owed much to the age-old problem of patch management. It exploited a Microsoft Windows vulnerability (MS08-67) that the Redmond software giant had actually issued a patch for a full 29 days before Conficker started to spread.

Conficker, as discussed above, also changed course numerous times, morphing from a worm running “headless” without a command and control (C&C) server, and spreading largely via network shares and USB sticks, to more modern variants where it would move laterally through the network, identifying weak and vulnerable devices.

“Most of the malware we see today doesn't spread via its own steam like the Conficker worm,” independent security analyst Graham Cluley said late last year.

“Instead malicious hackers write trojan horses that are designed to not draw attention to themselves, and are sometimes sent only to a small list of targets to improve their chances of infecting systems undetected and give attackers access to your files and communications.”

As of today, any good antivirus should now be able to detect and remove the worm, the only problem being the self-propagating nature of Conficker meaning computers infected with Conficker will go onto infect other PCs not running AV software.

What happened to the cybercriminals?

“Maybe the gang just decided that the botnet was being watched too closely by the security industry to accomplish anything.”

Oddly, little happened with these attacks, with ESET’s senior research fellow David Harley observing that “nothing seems to have been done” with the countless infected computers.

He wonders whether the malware, and the encompassing botnet, gained too much media attention: “Maybe the gang just decided that the botnet was being watched too closely by the security industry to accomplish anything.”

This is a view shared by Goretsky, who added: “With the world's anti-malware researchers watching it, and vigilantly reporting every move, it was hard for the criminal gang behind Conficker to do anything to monetize their worm.

“It was like thieves announcing they were going to rob a bank. Of course the police are going to respond to that sort of thing. It drew too much attention to itself, and that is what ultimately led to its failure, at least in terms of being used as a tool to commit further cybercrime.”

As of today, Conficker - and the people behind it - remain in obscurity. The criminal gang operating it appeared to abandon it towards the end of 2009. Yet, here we are, in 2016, still dealing with a worm that appears to have been left to its own devices.

Conficker, in many ways, remains a mystery but a vivid example of cybercrime and an ever-changing threat landscape.