by Perry Lynch
3:45 min read | Audio
Wireless access presents a special challenge for network security. A weak security implementation will allow intruders to gain an almost physical level of access; they may be able to bypass your firewall and directly connect to your information systems from locations that are within range of your facilities. CIS Control #15, "Wireless Access Control," provides guidance to minimize this risk.
The risk factors
Unmanaged wireless devices in the hands of trusted users present a significant risk: They provide access to information for trusted users, and are sometimes considered to be part of the network. However, they are not consistently managed or maintained, and are routinely exposed to malware and opportunities for corruption when they are not on your protected enterprise network.
To counter these risks, the access point should be considered as much a policy enforcement tool as it is a network gateway. Your network of access points should be maintained at current patch levels and at the highest possible encryption levels and configured to provide secured access to the enterprise network for corporately-owned devices. Guest devices, either staff or visitor-owned, should be restricted to a network segment or VLAN that provides access to the Internet only. To further limit risk, access points should also be configured to prevent ad-hoc wireless networking and direct client-to-client access within the Wireless LAN.
Configuring access points
The 802.11 security standard continue to evolve, with the launch of the WPA3 in the 2nd quarter of this year. The older security protocols, WEP and WPA, have known serious weaknesses and should no longer be used. The TKIP encryption protocol has been deprecated as well. The CIS recommendation is to use WPA2 with AES encryption. AES is the default when using WPA2 on modern devices.
Access point firmware needs to stay up to date. The KRACK vulnerability, discovered in 2017, affected virtually all WPA2 implementations. Manufacturers have issued firmware updates to address this issue; implementing these patches is necessary to maintain security.
If you are planning a future Wi-Fi implementation or upgrade, remember that vendors are submitting device designs for certification to the new protocol, with plans to fully support WPA3 in 2019. Make sure your hardware vendor will support a future-proof implementation to get the most from your investment.
Rogue access points
Unauthorized wireless access points can present a serious risk and should be removed from the network whenever they are discovered. Regardless of intent or configuration, they provide unauthorized and/or unprotected access to the network. Left unsecured, they could provide an unencrypted open access channel into your information assets.
Monitoring software that works from an inventory of authorized systems can recognize any unauthorized devices. This makes it possible to block the offending device from the network, then locate and disconnect it.
Many of the available managed access point solutions include Wireless Intrusion Detection Systems (WIDS) capabilities, providing the ability to detect and disable unauthorized access points or the use of various wireless attack tools.
Limiting other devices
Printers and other devices often include their own wireless access as a convenience feature. In a corporate environment, this should be disabled to prevent the printer from becoming an undocumented entry point to the network.
The use of Bluetooth in the environment is an often-overlooked concern: enabling unregulated pairings may permit intruders to gain direct access to computers on the network. Restricting Bluetooth-based services to only support headsets and input devices is easily handled with group policy and should be implemented whenever the environment contains Bluetooth-capable systems.
Limiting less trusted access
BYOD policies are useful but allowing personal devices to have unrestricted access to the same network your information systems rely on is never a great idea. Even with the most restrictive policies, the IT department doesn't have full administrative control over devices not owned by the organization. A reasonable compromise is to provide access to a guest VLAN, implement restrictive ACLS between it and the enterprise network, and permit out-bound only Internet access on that VLAN.
In any event, only wireless devices that are owned by the organization should be permitted on the enterprise network. This provides the IT staff with the authority to enforce adequate security restrictions for those devices.
Wireless networks provide value and convenience, but they require care and attention to avoid becoming a security problem. Facilities containing highly sensitive information assets should consider using it for guest access only or avoid using it at all. Enterprise networks that do use it need to employ the latest protocols, restrict its use to authorized devices, and be on the lookout for unauthorized access points.
by Perry Lynch
2:45 min read | Audio
The fewer ways there are to reach information, the less risk there is of unauthorized access. This is the point of CIS Control #14, "Controlled Access Based on the Need to Know." This is closely related to Control #13 "Data Protection," but focuses on the access allowed. The specific controls have some overlap, especially regarding encryption and logging. What is distinctive to this control is the emphasis on access control and network architecture.
Identify the Data
Data should be identified and automatically labeled or tagged based on the existing data classification requirements for your enterprise. This can be done using one of several active discovery tools that can investigate the network file shares and desktops to flag documents and folders that match the classification criteria. Upon identification, sensitive files can be relocated into the appropriate data file shares, ensuring that access rights and group policy are easier to maintain and govern.
Isolate the Data
Implementing VLANs for critical servers is a straightforward way to reduce the risk of compromise. Along with servers, VLANs should be configured to support other critical business functions. Micro segmentation should also be enabled, which restricts a user’s ability to directly connect between workstations on the network.
Implementing firewalls or ACLs between each VLAN will ensure that only authorized systems and protocols are permitted to communicate with each other and will significantly reduce the risk of unauthorized data exposure and/or the unchecked spread of malware within the enterprise.
Encrypt the Data
Implementing data encryption ensures that data compromise efforts are increased significantly. Encrypting data at rest for laptops, workstations in insecure environments, and servers containing sensitive data will mitigate against the risk of data compromise.
A mobile device management solution should be implemented for all corporate and user-provided mobile devices that will be permitted to access this data.
Encryption for data in transit should also be implemented for all methods: Transport Layer Security (TLS) should be required for all outbound email communications and for all web-based portals and user interfaces. Command Line access to management interfaces should be through SSH as well.
This mitigation strategy can be further strengthened by taking proper care to use a centralized key management system and to ensure that encryption algorithms and key sizes are reviewed and updated annually.
Protect the Data
Access to the systems containing sensitive data on the server VLAN should be restricted to specific groups of workstations within the network; file systems and database servers should also be restricted to specific groups of users.
User accounts should be configured with specific access rights based on their role within the organization. Administrative users should have two accounts, one with restricted access for normal work activities, and a separate admin-level account for any systems maintenance responsibilities.
Along with these controls, Data Loss Prevention should be implemented as a means of identifying and/or preventing the unauthorized exfiltration of data via USB, email, or web-based communications. DLP solutions typically rely on either common keywords or analysis of predefined data to identify, enforce, and report on policy violations.
Any system or account on the network carries some risk of being compromised. Any account or system with access to confidential data should be limited in order to reduce the chance of successful unauthorized access. Restricting access to critical resources and limiting the access rights of authorized systems and accounts will enable IT personnel to focus on detecting and preventing a smaller range of potential attacks.
by Perry Lynch
4:00 min read | Audio
Everything in systems security ultimately is about protecting data. CIS Control #13, deals with data protection in its most direct sense. The main issues are identifying sensitive data, preventing its unauthorized transfer, detecting any such transfers, and making improperly acquired data as difficult to use as possible.
Identifying critical data
The first step is to identify the data that needs protection. Organizations generally have their data spread over multiple systems with varying levels of security. However, you can successfully protect this data through the use of several tools and techniques: Access control, encryption, integrity protection, and data loss prevention can be used together to identify, restrict, and protect any sensitive or mission-critical data.
A data classification process should be undertaken. Once data is properly classified and labeled as regulated, sensitive, confidential, or public, those files and folders should then be migrated to properly identified folders on the SAN, and group policy should be applied to ensure that access is limited to authorized staff members.
Databases and files with sensitive data should be kept on machines which aren't exposed to outside connections. Access to them should also be restricted to authorized users on the internal network as well, in a manner that’s consistent with business requirements.
Once sensitive data is adequately secured, routine network hygiene needs to take place: Many users will maintain bad habits and keep unsecured copies of sensitive data because it's convenient. Administrators should routinely use appropriate tools to scan desktops and non-secured folders on the SAN for cleartext that looks like sensitive data and alert the appropriate data owners.
Protection by (and from) encryption
Laptops and mobile devices are easily stolen, so if they hold any sensitive information, the entire device needs encryption. Mobile Device Management tools can be used to secure sensitive corporate data for corporate and user-owned phones and smart devices, without impeding the end user’s personal use of the device. Full Disk Encryption should be deployed for all corporate laptops, using a centralized key management system. This will prevent unauthorized users from being able to access the device and any data should the laptop become lost or stolen.
Within the enterprise, encryption is often required in databases and other systems on the network. Many databases contain sensitive fields that require encryption or hashing, independently of the whether the disk is encrypted. Other systems may require the entire database be encrypted.
Methods of encryption need periodic review. Some algorithms that were once considered strong, such as SHA-1, are now deprecated because of their weaknesses. Any data encrypted using them needs migration to a better algorithm.
Encryption is valuable, but it's a problem when it isn't supposed to be happening. If outgoing encrypted traffic is originating from unauthorized desktops, it could be evidence of malware sneaking the data out. Network monitoring software can detect and flag the use of SSH and other secure protocols outside of expected contexts. If they don't have a legitimate purpose, administrators need to track down their source and remove any malware responsible.
Encrypted exfiltration can also tunnel through harmless-looking packets, such as DNS requests. These are harder to detect, but application-level monitoring software can often identify them by characteristics like abnormally long data fields.
Monitoring data movement
Network monitoring can generally recognize dubious packets. These packets could be included in otherwise legitimate traffic, such as an email that carries sensitive information in cleartext. It could indicate malware is at work, but it might also indicate that users are making otherwise legitimate transfers in an insecure way.
This falls into the area of data loss prevention (DLP). Software systems for DLP take a variety of approaches for recognizing abnormal traffic. Most rely on pattern detection, so human verification is generally necessary. Other systems rely on fingerprinting previously-identified data and will operate effectively with a lower level of human intervention. In either case, the software needs to be configured so that the number of false positives is reasonably low and, all alerts will get the attention they need.
Known hostile IP addresses should be blocked and monitored, as attempts to reach them could indicate that malware is trying to send out sensitive data; other destinations could be attempted if the first one is unreachable.
Transferring data within the network is sometimes a concern. Copying sensitive information to mobile phones or portable storage devices increases the risk. It may be a good idea to configure machines to prevent those transfers.
A large part of data protection is simply knowing where the information is and where it's going. Keeping track of all sensitive data storage and limiting its movement are essential practices, and accomplishing that requires safe network configurations, monitoring of traffic, encryption of data, and prompt action when problems arise. Protection needs to be multi-layered, especially when leaks would cause serious harm.
by Perry Lynch
3:30 min read | Audio
Defending network boundaries is an increasingly complicated and difficult task. Cloud services, remote access, and mobile devices can make it difficult to identify the exact boundaries of a network. CIS Control #12, which deals with the defense of network boundaries, is correspondingly complex. It pays to remember that boundary protection isn't just a matter of securing the front lines, it’s also a major component in a layered defense strategy.
Managing the task
Securing the boundaries means paying attention to new threats and attack methods and evaluating them against the needs of the business. Achieving a balance between effective security and user needs will require frequent risk analysis and constant communication with upper management. By doing so you will enable enforcement of an effective and realistic security plan that supports the business needs of your network.
A well-structured network architecture includes not just a DMZ for the limited number of Internet-facing systems, but also specific security zones for internal servers, systems management workstations, and other business-critical systems or applications.
Network scanning is necessary to make sure no one attempts an end run around the proxy. These might come from malware or from impatient users trying to circumvent the rules. Unauthorized VPN connections might send encrypted traffic through the proxy and present a security risk even if its purpose is relatively innocent.
Decryption of network traffic should take place at the proxy level. That lets it apply application-level security on top of IP and port filtering. The proxy will use whitelisting or blacklisting to prevent connections to malicious servers. Whitelisting is safer, but it's difficult to maintain a complete list of approved domains and IP addresses without constantly adding to it. Blacklisting requires constant updating from services that list rogue addresses.
Both inbound and outbound traffic needs filtering. Only ports and protocols that are considered mission-critical should be permitted outbound through the firewall. Additionally, blocking access to known malicious domains will defeat many phishing attempts. If malware can't reach a command and control server, it becomes far less effective, and easier to eliminate.
Intrusion prevention and detection
Preventing unauthorized activities and catching them as they happen are crucial to boundary protection. The Intrusion Detection/Prevention Systems (IDS/IPS) should be configured to alert and/or stop a majority of attempts by catching suspicious traffic. Signature-based detection is the traditional approach, but sandboxing and other methods can be considered as supplemental tools to detect zero-day attacks.
Monitoring should record the headers of any suspicious packets, if not the whole packet. This information is valuable for event monitoring, so that the source of the problem (external or internal) can be identified. Analytics run on this information can turn up patterns that are too subtle to detect from a small sample.
Malicious traffic can piggyback on all kinds of protocols to escape notice. For instance, if large numbers of senseless DNS requests are being sent out, they may cloak communication with a hostile server. For this reason, DNS queries should only be permitted to trusted external servers, many of whom can provide filtering services to further limit the ability to introduce malware to the network.
Security would be simpler if the entire network were physically behind the router and firewall. However, most businesses find that allowing remote access increases productivity and improves employee satisfaction. The amount of control IT management can exercise over these devices is generally less.
The CIS control recommends requiring all remote access to use two-factor authentication for logins. If those devices fall into the wrong hands or if someone steals the password, an additional factor such as a token or a text message will make it harder for them to take advantage of it.
If the business lends devices for use outside the office, it should set up remote device management for them. This will ensure they stay up to date on patches and have a secure configuration. In the case of cell phones and other smart devices, it should include remote wiping. BYOD devices should meet company-set security standards before getting access.
Business partners that connect to the network can be a serious risk if they don't observe high security standards. The business needs to specify security standards which connected partners have to meet, then monitor their access.