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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
ServerIron ADX Security Guide 1
53-1002440-03
Chapter
1
Network Security
TCP SYN attacks
ServerIron software contains many intrusion detection and prevention capabilities. The ServerIron
can be configured to defend against a variety of TCP SYN attacks, Denial of Service (DoS) attacks,
and Smurf attacks.
TCP SYN attacks disrupt normal traffic flow by exploiting the way TCP connections are established.
When a normal TCP connection occurs, the connecting host first sends a TCP SYN packet to the
destination host. The destination host (actually the ServerIron, acting as an intermediary between
the source and destination hosts) responds with a SYN ACK packet. The connecting host then
returns an ACK packet. This process, known as a “TCP three-way handshake”, establishes the TCP
connection.
A TCP SYN attack floods a host with TCP SYN packets. For each of these TCP SYN packets, the
ServerIron responds with a SYN ACK packet and adds an entry to its session table. However, no
ACK packet is actually sent back, so the connection is incomplete. If the attacker sends enough
TCP SYN packets, the session table fills up with incomplete connections, and service can be denied
to legitimate TCP connections.
syn-proxy
IP TCP syn-proxy
Configure the ip tcp syn-proxy command as shown in the following.
1. Configure syn-proxy in the global mode.
ServerIronADX(config)# ip tcp syn-proxy
Syntax: ip tcp syn-proxy
NOTE
You must configure ip tcp syn-proxy command only at the global level, to turn on and off the
global syn-proxy flag.
2. Enable syn-proxy on each interface handling inbound SYN requests (no change here).
ServerIronADX(config)#interface e 3/1
ServerIronADX(config-if-3/1)# ip tcp syn-proxy in
Usage guidelines:
• The default value for a valid ACK time is 32 seconds and is not user configurable.
• If you enter a value, it is ignored. The command remains in the config file the way you enter it,
in case you need to downgrade to the previous release.