Critical Measures to Keep Your PACS Secure

A recent article by a McAfee employee stated that more than 1100 PACS systems are currently exposed to the public internet and can be relatively easily accessed to the extent that intruders can retrieve and upload images with few problems. In doing research for his article, he did just that. The fact that certain image files were accessed is troublesome by itself. Even more troubling, medical data was changed. We wonder if someone is paying attention at those sites or if McAfee notified them.

According to HIPAA, if patient data is seen by someone who should not see it, federal law requires doctors, hospitals, and other health care providers to notify those patients of a “breach” of their health information. Patients in turn can file a complaint with the HHS office for Civil Rights (OCR). But, independent from privacy and possibly even ethical questions about this particular experiment, the fact remains that 7% of all PACS systems are completely unprotected.

What does it mean that a system is secure? According to a recent MITA white paper called “Cyber Security for Medical Imaging”:  A device can be considered secure if it defends unintended or unauthorized operation with respect to its intended environment and its intended use—as specified by its manufacturer. Therefore, providing security measures in the device and also infrastructure is a key requirement.

Security for medical devices also got the attention of the FDA. A premarket notification or 510(k) approval for PACS systems has to include a security assessment otherwise it won’t be cleared for use by the FDA. The premarket submission requires several additional documents addressing the security aspects.

Security is not only a PACS issue. At the HIMSS 2018 conference that just wrapped up in Las Vegas, the organization released its annual cybersecurity survey of its 70,000 health IT professionals showing that 75% of the respondents had experienced a recent significant security incident.

Now, back to what you can do to protect your PACS system. Below are the most important measures you can take to guard against internal and external security threats. It consists of three major phases: Identify, Mitigate, and Monitor and Review.

1. Identify the Threats

  • Inventory your systems – Know your “surface area” for attack. Many times the weak link is an open workstation at a specialist’s office or a modality hidden in an OR that nobody checked. Remember to include your wireless systems as well. The increased connectivity within the enterprise of new specialties, POC ultrasounds and other imaging input and output devices being used by physicians create additional challenges for security.
     
  • Conduct a security review – Engage an outside auditor to review your systems and conduct penetration testing. Audit your systems’ compliance with the HIPAA Security Rule and PCI standards. PCI applies to payment systems, not healthcare, but they have many relevant and helpful guidelines. Even if you have a strong security team in-house, it helps to have an unbiased “outsider” to review your security plan.
     
  • Manage your vendor access – Vendors typically access their products as part of their service contracts, which means you could have multiple access points in your PACS. For example, one for the PACS server vendor, several for your modalities, which can be from a couple of different vendors, and you might have third party software for 3-D or other applications, as well as a speech recognition vendor, etc. Make sure that vendor access is limited to their device only and, most importantly, monitor it, i.e. check the audit trails and access logs. You want to know who accessed your devices and when, in case there are issues. It would not be the first time that a vendor made changes corrupting a database, upgrading a software release, installing patches, etc. without notifying the customer.
     

2. Mitigate the Threats

  • Switch off the promiscuous mode on your devices – Almost every PACS server has a “poor man’s” security mechanism, by which an unknown DICOM application, identified by a DICOM AE-Title that is not in its configuration file, is refused a connection at the Application level aka Association. However, if you have configured your PACS to be “promiscuous,” meaning that it will talk to any AE-Title, it will connect and potentially allow the upload or retrieval of data. The advantage of operating in a promiscuous mode is that every time a new device needs to be connected, you don’t have to change the configuration, however this is very poor practice.
     
  • Manage access configuration – PACS systems often have some granularity with regard to these privileges, for example, it might allow any device to query its database, but not allow images to be retrieved. If you look at some of the PACS user groups, this is probably one of the top-ten most asked questions: “Why can I not retrieve images from the PACS despite the fact that I can communicate with it.” The answer is that you need to add it to the access configuration file. Manage this access and configuration yourself as a PACS administrator; don’t rely on the vendor to do this for you.
     
  • Map any connected device to its port and IP address – As part of the access configuration file, most PACS systems will also keep track of who is connecting from what IP address and port number (hence the requirement to have fixed IP addresses using the DICOM protocol). If a device with a known AE-Title suddenly tries to access the server from another IP or to a different port, it should refuse the connection. Again, manage this configuration.
     
  • Use standard port numbers not port 104! – For security, DICOM applications should run in user mode without root access. Port numbers below 1024 are privileged ports that require root access by the application. The Internet Assigned Numbers Authority (IANA) has assigned a standard “registered” port number of 11112 that should be used rather than the well-known port 104.
     
  • Secure your perimeter – Use standard IT security best practices to harden your exposure to the outside, such as:
     
    1. Use a professional firewall – A Stateful Inspection Firewall can analyze packets down to the application layer. The simple packet filtering firewall you find in most routers is not effective against a determined hacker.
    2. Deny-first – Restrict access with a deny-first firewall policy, then whitelist systems and IP addresses that need access.
       
    3. Use intrusion detection systems (IDS) – An IDS can spot hacking attempts in real-time. An IDS can log and alert you when suspicious actions occur, like the administrative credentials logging into the EHR system at 3:00 a.m.
       
    4. Use Proxies and Routers – Proxy and router systems from vendors such as DICOM Systems, MedWeb, RamSoft, Osimis, Laurel Bridge and others sit between your PACS and outside systems. These proxies can automate encryption, authentication, anonymization, and more. They provide a security wrapper for DICOM devices to manage the limitations of the DICOM standard. When selecting a proxy system, it’s wise to use a professional vendor. Don’t try to roll-your-own security.
       
  • Use VPNs for remote access – If you must allow direct access to PACS, use a Virtual Private Network (VPN). These can be complicated to implement and require a knowledgeable IT staff to manage. Don’t be tempted to skip this and trust a password to protect your open ports. Your password will be broken or leaked.
     
  • Segment your network – Segment your network using Virtual LANs (VLAN) and demilitarized zones (DMZ) where appropriate. Put your public-facing servers in a DMZ. An attacker gaining control of these servers will have limited surface area to attack your internal systems. Use VLANs to segment departments where possible. There is no reason for the shipping computers on the loading dock to have direct IP access to the DICOM network systems.
     
  • Control access by removable devices – TechAdvisory.org has reported that 25 percent of malware is transferred through USB, therefore, you can eliminate this risk by simply not allowing unauthorized USB drives in secure networks. This protects you by restricting unauthorized data exfiltration and by cutting off a vector for malware intrusion. Disabling the USB ports is easy to do in Windows as an administrator. You can disable USB removable media across the entire domain via Active Directory Group Policy. Remember that this applies to your service providers as well, the last thing you want to have happen is allow a service engineer who just picked up a virus from a “dirty” site to use the same flash drive to infect your network (this happens!)
     

3. Monitor and Review

  • Check your audit trails – Audit trails for application level access are a HIPAA requirement. If you never look at them, they might as well not be implemented. Regular audits help detect both internal and external access violations of patient data. There are no “standard” guidelines on how often to check the audit trails, but most people we talk with seem to do it once a week, checking random accesses from random people. Support for standard audit trails is important, IHE defines a ATNA profile that provides this information to be recorded in a standard format. Check your IHE integration statement of your PACS system. Further transformation of your audit trails into XES event logs can facilitate process mining.
     
  • Rinse and Repeat – Go back to step 1. Inventory, audit and conduct reviews. This is a continuous process. You’ll never be finished, but you can be assured that you put the right practices in place.
     

Will these measures protect your PACS? As many security professionals will tell you, nothing is 100% secure. If someone really wants to get access to your data and/or modify it, there is likely a way. But instead of leaving the front door wide open and put your family jewels on the kitchen table, you can at least have a locked, security system and add another perimeter to secure it, so that potential hackers or intruders will go looking for an easier target.

Herman Oosterwijk is president of OTech and a PACS, DICOM, HL7 trainer/consultant, David Finster consults on security and data protection best practices. We encourage comments.