A stolen cache of files that may belong to the National Security Agency contains genuine hacking tools that not only work, but show a level of sophistication rarely seen, according to security researchers.That includes malware that can infect a device\u2019s firmware and persist, even if the operating system is reinstalled. \u00a0\u201cIt's terrifying because it demonstrates a serious level of expertise and technical ability,\u201d said Brendan Dolan-Gavitt, an assistant professor at New York University\u2019s school of engineering.He\u2019s been among the researchers going over the sample files from the cache, after an anonymous group called the Shadow Brokers posted them online.Allegedly, the files were stolen from the Equation Group, a top cyberespionage team that may be connected with the NSA.The Equation Group likely helped develop the infamous Stuxnet computer worm, and is said to have created malware that can be impossible to remove once installed.Already, researchers have found that the hacking tools inside the sample files target firewall and router products and do so by exploiting software flaws \u2013 some of which could be zero-day vulnerabilities or defects that have never been reported before.On Wednesday, Cisco confirmed that the sample files did contain one unknown flaw that affects the company\u2019s firewall software, and a patch has been rolled out.Other affected vendors including Juniper Networks say they are still studying the matter, but more patches will likely come. \u00a0Brian Martin, a director at Risk Based Security, has been studying the sample files as well and said they also target possible zero-day vulnerabilities in Chinese products, including those from firewall provider Topsec.However, the hacks may not be as dangerous as researchers initially feared. For instance, the exploits found within the samples rely on having direct access to the firewall\u2019s interface, which is normally restricted from outside Internet users, Martin said.\u201cThe exploits are still useful, but they\u2019re not what people dreaded,\u201d he added. \u00a0Nevertheless, the hacking tools probably weren\u2019t easy to develop. Within the sample files are also pieces of malware that can target a computer\u2019s firmware called the BIOS, Dolan-Gavitt said.\u201cThe BIOS is the first piece of code that runs when a system boots, and so it has control over everything else,\u201d he added.As a result, any malware installed on the BIOS, will continue to persist even if the computer\u2019s operating system is reinstalled. That can make it particularly useful to spy on a computer\u2019s network traffic or inject new data.However, to develop malware, the creators would have needed detailed knowledge on the hardware, Dolan-Gavitt said. Normally this isn\u2019t made publicly available, so the creators may have resorted to reverse-engineering.The BIOS malware appears to affect Cisco products, but on Wednesday the company said that it had already patched the issue through its Secure Boot startup process.