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Table Of Contents
- Contents
- About This Document
- Network Security
- TCP SYN attacks
- IP TCP syn-proxy
- Granular application of syn-proxy feature
- Syn-def
- No response to non-SYN first packet of a TCP flow
- Prioritizing management traffic
- Peak BP utilization with TRAP
- Transaction Rate Limit (TRL)
- Understanding transaction rate limit
- Configuring transaction rate limit
- Configuring the maximum number of rules
- Saving a TRL configuration
- Transaction rate limit command reference
- Global TRL
- TRL plus security ACL-ID
- security acl-id
- Transaction rate limit hold-down value
- Displaying TRL rules statistics
- Displaying TRL rules in a policy
- Displaying IP address with held down traffic
- Refusing new connections from a specified IP address
- HTTP TRL
- Overview of HTTP TRL
- Configuring HTTP TRL
- Displaying HTTP TRL
- Display all HTTP TRL policies
- Display HTTP TRL policy from index
- Display HTTP TRL policy client
- Display HTTP TRL policy starting from index
- Display HTTP TRL policy matching a regular expression
- Display HTTP TRL policy client index (MP)
- Display HTTP TRL policy client index (BP)
- Display HTTP TRL policy for all client entries (BP)
- Downloading an HTTP TRL policy through TFTP
- HTTP TRL policy commands
- Logging for DoS Attacks
- Maximum connections
- clear statistics dos-attack
- Maximum concurrent connection limit per client
- Firewall load balancing enhancements
- Syn-cookie threshhold trap
- Service port attack protection in hardware
- Traffic segmentation
- DNS attack protection
- Access Control List
- How ServerIron processes ACLs
- Default ACL action
- Types of IP ACLs
- ACL IDs and entries
- ACL entries and the Layer 4 CAM
- Configuring numbered and named ACLs
- Modifying ACLs
- Displaying a list of ACL entries
- Applying an ACLs to interfaces
- ACL logging
- Dropping all fragments that exactly match a flow-based ACL
- Enabling ACL filtering of fragmented packets
- Enabling hardware filtering for packets denied by flow-based ACLs
- Enabling strict TCP or UDP mode for flow-based ACLs
- ACLs and ICMP
- Using ACLs and NAT on the same interface (flow-based ACLs)
- Displaying ACL bindings
- Troubleshooting rule-based ACLs
- IPv6 Access Control Lists
- Network Address Translation
- Syn-Proxy and DoS Protection
- Understanding Syn-Proxy
- Configuring Syn-Proxy
- DDoS protection
- Configuring a security filter
- Configuring a Generic Rule
- Configuring a rule for common attack types
- Configuring a rule for ip-option attack types
- Configuring a rule for icmp-type options
- Configuring a rule for IPv6 ICMP types
- Configuring a rule for IPv6 ext header types
- Binding the filter to an interface
- Clearing DOS attack statistics
- Clearing all DDOS Filter & Attack Counters
- Logging for DoS attacks
- Displaying security filter statistics
- Address-sweep and port-scan logging
- Secure Socket Layer (SSL) Acceleration
- SSL overview
- SSL acceleration on the ServerIron ADX
- Configuring SSL on a ServerIron ADX
- Basic SSL profile configuration
- Advanced SSL profile configuration
- Configuring Real and Virtual Servers for SSL Termination and Proxy Mode
- Configuration Examples for SSL Termination and Proxy Modes
- SSL debug and troubleshooting commands
- Displaying socket information
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Chapter
5
Syn-Proxy and DoS Protection
This chapter describes how to configure Syn-Proxy and DOS protection features on the ServerIron
ADX Traffic Managers.
Understanding Syn-Proxy
Syn-Proxy™ allows TCP connections to be terminated on the ServerIron ADX. When Syn-Proxy is
enabled, the ServerIron ADX completes the three-way handshake with a connecting client. Only
when the three-way handshake is completed does the ServerIron ADX establish a connection with
the destination server and forward packets from the client to the server.
In a TCP SYN attack, the attacker floods a host with TCP SYN packets. The host replies with
SYN-ACK packets, but the attacker does not send the ACK packet. The handshake remains
incomplete, and the host goes into a perpetual wait-state for it to be completed. As a result, the
resources available for TCP connections are rapidly depleted and the host is unable to accept any
further TCP connections.
ServerIron ADX prevents these types of attacks by sitting in between the host and attacker. When
an attacker sends the SYN packet, ServerIron ADX receives it and replies to it with SYN-ACK. If the
attacker doesn’t send an ACK to the ServerIron ADX, the handshake isn’t completed with the
ServerIron ADX. In this situation, the server never receives any packets from the attacking client
and is oblivious to the attack.
If the SYN is from a valid client and not an attacker, ServerIron ADX completes the handshake and
forwards the SYN to the host. ServerIron ADX creates a session at this time; only when the
three-way handshake is complete.
NOTE
In software syn-proxy, throughput for syn-attack is 1.18Mbps per core.
Syn-Proxy auto control
Syn-Proxy can be explicitly enabled or disabled through a CLI command or setup to be
automatically enabled when the TCP SYN packet arrival rate exceeds a configured threshold or
disabled when the TCP SYN packet arrival rate falls below a configured threshold.
Difference between ServerIron ADX and JetCore Syn-Proxy Behavior
ServerIron ADX and JetCore-based ServerIron devices show different behavior with TCP Syn-Proxy.
A ServerIron ADX drops TCP SYN ACKs entering an interface where tcp syn-proxy is configured
unless it can match those SYN ACKs to an existing session. The JetCore-based ServerIron devices
forward them through. The behaviour of the ServerIron ADX provides enhanced protection against
SYN attacks relative to the protection available from JetCore-based ServerIron devices.