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XCCDF
SEL-2740S L2S Security Technical Implementation Guide
SEL-2740S L2S Security Technical Implementation Guide
An XCCDF Benchmark
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13 rules organized in 13 groups
SRG-NET-000512-L2S-000028
1 Rule
The SEL-2740S must be configured to mitigate the risk of ARP cache poisoning attacks.
Medium Severity
The SEL-2740S must deter ARP cache poisoning attacks and configure the specific ARP flows that are only necessary to the control system network.
SRG-NET-000512-L2S-000029
1 Rule
The SEL-2740S must be configured to capture all packets without flow rule match criteria.
Medium Severity
The OTSDN switch must be capable of capturing frames that are not engineered to be in the network and send them to a Security Information and Event Manager (SIEM) or midpoint sensor for analysis.
SRG-NET-000512-L2S-000030
1 Rule
The SEL-2740S must be configured with backup flows for all host and switch flows to ensure proper failover scheme is in place for the network.
Medium Severity
The SEL-2740S must be capable of multiple fast failover, backup and in cases isolation of the traffic from a detected threat in the system.
SRG-NET-000512-L2S-000031
1 Rule
The SEL-2740S must be configured to forward only frames from allowed network-connected endpoint devices.
Medium Severity
By only allowing frames to be forwarded from known end-points mitigates risks associated with broadcast, unknown unicast, and multicast traffic storms.
SRG-NET-000131-L2S-000014
1 Rule
The SEL-2740S must be configured to permit the allowed and necessary ports, functions, protocols, and services.
Medium Severity
A compromised switch introduces risk to the entire network infrastructure as well as data resources that are accessible via the network. The perimeter defense has no oversight or control of attacks by malicious users within the network. Preventing network breaches from within is dependent on implementing a comprehensive defense-in-depth strategy, including securing each device connected to the network. This is accomplished by following and implementing all security guidance applicable for each node type. A fundamental step in securing each switch is to enable only the capabilities required for operation.
SRG-NET-000193-L2S-000020
1 Rule
The SEL-2740S -must be configured to limit excess bandwidth and denial of service (DoS) attacks.
Medium Severity
Denial of service is a condition when a resource is not available for legitimate users. Packet flooding DDoS attacks are referred to as volumetric attacks and have the objective of overloading a network or circuit to deny or seriously degrade performance, which denies access to the services that normally traverse the network or circuit. Volumetric attacks have become relatively easy to launch by using readily available tools such as Low Orbit Ion Cannon or by using botnets. Measures to mitigate the effects of a successful volumetric attack must be taken to ensure that sufficient capacity is available for mission-critical traffic. Managing capacity may include, for example, establishing selected network usage priorities or quotas and enforcing them using rate limiting, Quality of Service (QoS), or other resource reservation control methods. These measures may also mitigate the effects of sudden decreases in network capacity that are the result of accidental or intentional physical damage to telecommunications facilities (such as cable cuts or weather-related outages).
SRG-NET-000331-L2S-000001
1 Rule
The SEL-2740S must be configured to packet capture flows.
Medium Severity
Without the capability to select a user session to capture/record or view/hear, investigations into suspicious or harmful events would be hampered by the volume of information captured. The volume of information captured may also adversely impact the operation for the network. Session audits may include port mirroring, tracking websites visited, and recording information and/or file transfers.
SRG-NET-000332-L2S-000002
1 Rule
The SEL-2740S must be configured to capture flows for real-time visualization tools.
Medium Severity
Without the capability to remotely view/hear all content related to a user session, investigations into suspicious user activity would be hampered. Real-time monitoring allows authorized personnel to take action before additional damage is done. The ability to observe user sessions as they are happening allows for interceding in ongoing events that after-the-fact review of captured content would not allow.
SRG-NET-000362-L2S-000024
1 Rule
The SEL-2740S must be configured to prevent packet flooding and bandwidth saturation.
Medium Severity
Access layer switches use the Content Addressable Memory (CAM) table to direct traffic to specific ports based on the VLAN number and the destination MAC address of the frame. When a router has an Address Resolution Protocol (ARP) entry for a destination host and forwards it to the access layer switch and there is no entry corresponding to the frame's destination MAC address in the incoming VLAN, the frame will be sent to all forwarding ports within the respective VLAN, which causes flooding. Large amounts of flooded traffic can saturate low-bandwidth links, causing network performance issues or complete connectivity outage to the connected devices. Unknown unicast flooding has been a nagging problem in networks that have asymmetric routing and default timers. To mitigate the risk of a connectivity outage, the Unknown Unicast Flood Blocking (UUFB) feature must be implemented on all access layer switches. The UUFB feature will block unknown unicast traffic flooding and only permit egress traffic with MAC addresses that are known to exit on the port.
SRG-NET-000362-L2S-000026
1 Rule
SEL-2740S flow rules must include the host IP addresses that are bound to designated SEL-2740S ports for ensuring trusted host access.
Medium Severity
IP Source Guard provides source IP address filtering on a Layer 2 port to prevent a malicious host from impersonating a legitimate host by assuming the legitimate host's IP address. The feature uses dynamic DHCP snooping and static IP source binding to match IP addresses to hosts on untrusted Layer 2 access ports. Initially, all IP traffic on the protected port is blocked except for DHCP packets. After a client receives an IP address from the DHCP server, or after static IP source binding is configured by the administrator, all traffic with that IP source address is permitted from that client. Traffic from other hosts is denied. This filtering limits a host's ability to attack the network by claiming a neighbor host's IP address.
SRG-NET-000362-L2S-000027
1 Rule
The SEL-2740S must be configured with ARP flow rules that are statically created with valid IP-to-MAC address bindings.
Medium Severity
DAI intercepts Address Resolution Protocol (ARP) requests and verifies that each of these packets has a valid IP-to-MAC address binding before updating the local ARP cache and before forwarding the packet to the appropriate destination. Invalid ARP packets are dropped and logged. DAI determines the validity of an ARP packet based on valid IP-to-MAC address bindings stored in the DHCP snooping binding database. If the ARP packet is received on a trusted interface, the switch forwards the packet without any checks. On untrusted interfaces, the switch forwards the packet only if it is valid.
SRG-NET-000343-L2S-000016
1 Rule
The SEL-2740S must authenticate all network-connected endpoint devices before establishing any connection.
Medium Severity
Without authenticating devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity. For distributed architectures (e.g., service-oriented architectures), the decisions regarding the validation of authentication claims may be made by services separate from the services acting on those decisions. In such situations, it is necessary to provide authentication decisions (as opposed to the actual authenticators) to the services that need to act on those decisions. This requirement applies to applications that connect either locally, remotely, or through a network to an endpoint device (including, but not limited to, workstations, printers, servers (outside a datacenter), VoIP Phones, and VTC CODECs). Gateways and SOA applications are examples of where this requirement would apply. Device authentication is a solution enabling an organization to manage devices. It is an additional layer of authentication ensuring only specific pre-authorized devices can access the system.
SRG-NET-000148-L2S-000015
1 Rule
The SEL-2740S must uniquely identify all network-connected endpoint devices before establishing any connection.
High Severity
Controlling LAN access via identification of connecting hosts can assist in preventing a malicious user from connecting an unauthorized PC to a switch port to inject or receive data from the network without detection.