Sophos Tracks Nefilim And Other Ransomware Attacks to “Ghost” Account Credentials

Sophos Press Release

OXFORD, U.K. – Jan. 26, 2021 – Sophos, a global leader in next-generation cybersecurity, today published its latest findings into real world attacks investigated by its Rapid Response team. The article, “Nefilim Ransomware Attack Uses ‘Ghost’ Credentials,” details how a failure to keep close tabs on “ghost” account credentials facilitated two recent cyberattacks, one of which involved Nefilim ransomware.

Nefilim, also known as Nemty ransomware, combines data theft with encryption. The target hit by Nefilim had more than 100 systems impacted. Sophos responders traced the initial intrusion to an admin account with high level access that attackers had compromised more than four weeks before they released the ransomware. During this time, the attackers were able to quietly move through the network, steal credentials for a domain admin account, and find and exfiltrate hundreds of GB of data, before unleashing the ransomware that revealed their presence.

The hacked admin account that enabled this belonged to an employee who had sadly passed away around three months previously. The company had kept the account active because it was used for a number of services.

In the second, unrelated attack, Sophos responders found that intruders had created a new user account and added it to the target’s domain admin group in Active Directory. With this new new domain admin account, the attackers were able to delete approximately 150 virtual servers and encrypt the server backups using Microsoft Bitlocker – all without setting off alerts.

“If it wasn’t for the ransomware that flagged the presence of intruders, how long might the attackers have had domain admin access to the network without the company knowing?” said Peter Mackenzie, manager, Sophos Rapid Response. “Staying on top of account credentials is basic, but critical cybersecurity hygiene. We see far too many incidents where accounts have been set up, often with considerable access rights, that are then forgotten about, sometimes for years. Such ‘ghost’ accounts are a prime target for attackers.

“If an organization really needs an account after someone has left the company, they should implement a service account and deny interactive logins to prevent any unwanted activity. Or, if they don’t need the account for anything else, disable it and carry out regular audits of Active Directory.

“The danger is not just keeping outdated and unmonitored accounts active; it is also giving employees greater access rights than they need. Fewer accounts need to be a domain admin than most people think. No account with privileges should be used by default for work that doesn't require that level of access. Users should elevate to using the required accounts when needed and only for that task. Further, alerts should be set so that if the domain admin account is used or if a new admin account is created, someone knows.” 

Nefilim ransomware was first reported on in March 2020. Like other ransomware families such as Dharma, Nefilim mainly targets vulnerable Remote Desktop Protocol (RPD) systems as well as exposed Citrix software. It is one of a growing number of ransomware families, alongside DoppelPaymer and others that engages in so-called “secondary extortion,” with attacks that combine encryption with data theft and the threat of public exposure.

Further information on the incidents, including Indicators of Compromise (IoCs) and tactics, techniques and procedures (TTPs) for the Nefilim attack, can be found in “Nefilim Ransomware Attack Uses ‘Ghost’ Credentials.

Ransomware timeline



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Sophos 是先进网络安全解决方案的全球领导者和创新者,包括托管式侦测与响应 (MDR) 和事件响应服务,各种端点、网络、电子邮件和云安全技术,帮助企业防御网络攻击。作为最大的纯网络安全供应商之一,Sophos 帮助全球超过 500,000 家企业和超过 1 亿用户抵御主动攻击对手、勒索软件、网络钓鱼、恶意软件等。Sophos 的服务和产品通过 Sophos Central 云管理控制台连接,并得到内部跨领域威胁情报部门 Sophos X-Ops 的支持。Sophos X-Ops 情报优化整个 Sophos Adaptive Cybersecurity Ecosystem 自适应网络安全生态体系,包括一个中央数据湖,为客户、合作伙伴、开发人员和其他网络安全与信息技术供应商提供一组丰富的开放 API。Sophos 为需要全托管并即使可用的安全解决方案的企业提供网络安全即服务,客户还可以直接利用 Sophos 的安全运行平台管理其网络安全,或者采用混合方法,为内部团队补充 Sophos 服务(包括威胁追踪与修复)。Sophos 通过世界各地的经销商合作伙伴和托管服务供应商 (MSP) 销售。Sophos 总部位于英国牛津。如欲了解更多信息,请访问 www.sophos.com