Apple 034-2351_Cvr DNS Service Profiling, Denial-of-Service DoS, To alter BIND’s version response

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With a copy of your master zone, the hacker can see what kinds of services a domain offers, and the IP address of the servers that offer them. He or she can then try specific attacks based on those services. This is reconnaissance before another attack.

To defend against this attack, you need to specify which IP addresses are allowed to request zone transfers (your slave zone servers) and disallow all others. Zone transfers are accomplished over TCP on port 53. The method of limiting zone transfers is blocking zone transfer requests from anyone but your slave DNS servers.

To specify zone transfer IP addresses:

mCreate a firewall filter that allows only IP addresses inside your firewall to access TCP port 53.

Follow the instructions in “Creating an Advanced IP Filter for TCP ports” in Chapter 3, “IP Firewall Service.” Use the following settings:

•Allow packet.

•Port 53.

•TCP protocol.

•Source IP is the IP address of your slave DNS server.

•Destination IP is the IP address of your master DNS server.

DNS Service Profiling

Another common reconnaissance technique used by malicious users is to profile your DNS Service. First a hacker makes a BIND version request. The server will report what version of BIND is running. He or she then compares the response to known exploits and vulnerabilities for that version of BIND.

To defend against this attack, you can configure BIND to respond with something other than what it is.

To alter BIND’s version response:

1Launch a command-line text editor (like vi, emacs, or pico).

2Open named.conf for editing.

3Add the following to the “options” brackets of the configuration file.

version

"[your text, maybe ‘we're not telling!’]";

4Save the config file.

Denial-of-Service (DoS)

This kind of attack is very common and easy to do. A hacker sends so many service requests and queries that a server uses all of its processing power and network bandwidth to try and respond. The hacker prevents legitimate use of the service by overloading it.

Chapter 2 DNS Service

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Contents Mac OS X Server Network Services Administration 034-2351/9-20-03 Contents Glossary Index Using This Guide How to Use This GuideWhat’s Included in This Guide Getting Help for Everyday Management Tasks Setting Up Mac OS X Server for the First TimeGetting Additional Information Before You Set Up Dhcp Service Dhcp ServiceLocating the Dhcp Server Using Static IP AddressesCreating Subnets Assigning IP Addresses DynamicallyAssigning Reserved IP Addresses Setting Up Dhcp Service for the First TimeUsing Multiple Dhcp Servers on a Network Interacting With Other Dhcp ServersSet up logs for Dhcp service Managing Dhcp ServiceStarting and Stopping Dhcp Service Creating Subnets in Dhcp ServiceTo change subnet settings Changing Subnet Settings in Dhcp ServiceSetting the DNS Server for a Dhcp Subnet Deleting Subnets From Dhcp ServiceChanging IP Address Lease Times for a Subnet Setting Wins Options for a Subnet Setting Ldap Options for a SubnetTo set Ldap options for a subnet Disabling Subnets Temporarily Monitoring Dhcp ServiceViewing the Dhcp Status Overview Viewing Dhcp Log Entries Setting the Log Detail Level for Dhcp ServiceViewing the Dhcp Client List Where to Find More Information DNS Service DNS and Bind Before You Set Up DNS ServiceSetting Up DNS Service for the First Time Setting Up Multiple Name ServersLearn and plan Start DNS service Configure basic DNS settingsSet up a mail exchange MX record optional Configure the reverse lookup zone optionalEnabling or Disabling Recursion Managing DNS ServiceStarting and Stopping DNS Service Enabling or Disabling Zone TransfersAdding a Master Zone Managing ZonesTo add a master zone Adding a Slave ZoneTo add a slave zone To duplicate a zone Adding a Forward ZoneDuplicating a Zone To add a forward zoneTo modify a zone Managing RecordsModifying a Zone Deleting a ZoneTo add a record Adding a Record to a ZoneTo delete a record Modifying a Record in a ZoneDeleting a Record From a Zone To modify a recordViewing DNS Log Entries Viewing DNS Service StatusViewing DNS Service Activity Monitoring DNSViewing DNS Usage Statistics Changing DNS Log File LocationTo change the log detail level To see DNS usage statistics Securing the DNS ServerDNS Spoofing Server MiningTo alter BIND’s version response DNS Service ProfilingDenial-of-Service DoS To specify zone transfer IP addressesService Piggybacking Setting Up MX Records Common Network Administration Tasks That Use DNS ServiceExample.com Edit the MX record of the primary mail server Configuring DNS for Mail ServiceTo enable MX records Enabling Redundant Mail ServersTo enable backup or redundant mail servers Setting Up Namespace Behind a NAT RouterNetwork Load Distribution aka Round Robin Setting Up a Private TCP/IP NetworkHosting Several Internet Services With a Single IP Address Configuring Bind Using the Command LineWhat Is BIND? Zone Data Files Bind Configuration FileBind on Mac OS X Server Practical ExampleTo set up the sample files Setting Up Sample Configuration FilesConfiguring Clients If you are using Mac OS X Server as your Dhcp Server Using DNS With Dynamically Assigned IP AddressesCheck Your Configuration Request For Comment Documents For more information on DNS and BIND, see the followingPage IP Firewall Service IP Firewall Service Subnet Mask What is a Filter?Understanding Firewall Filters IP AddressCidr Rule Mechanism and Precedence Using Address RangesMultiple IP Addresses Add filters to the IP filter list Setting Up Firewall Service for the First TimeStart firewall service Create an IP address group that filters will apply toSave firewall service changes Managing Firewall ServiceStarting and Stopping Firewall Service Opening the Firewall for Standard ServicesCreating an Address Group To open the firewall for standard servicesTo create an address group To edit or delete an address group Editing or Deleting an Address GroupDuplicating an Address Group Creating an Advanced IP Filter for TCP portsTo create an IP filter for TCP ports Creating an Advanced IP Filter for UDP PortsTo create an IP filter for UDP ports NFSTo edit advanced IP filters Changing the Default FilterTo change the Default setting Editing Advanced IP FiltersViewing the Firewall Log Monitoring Firewall ServiceSetting Up Logs for Firewall Service Viewing the Firewall Status OverviewTo view denied packets Viewing Denied PacketsViewing Packets Logged by Filter Rules Log ExampleTo do this Block Access to Internet UsersPractical Examples Block Junk MailAllow a Customer to Access the Apple File Server To prevent ping denial-of-service attacks Preventing Denial-of-Service DoS AttacksControlling or Enabling Peer-to-Peer Network Usage Controlling or Enabling Network Game Usage Advanced ConfigurationBackground Creating IP Filter Rules Using ipfw PrecautionsCreating IP Filter Rules Reviewing IP Filter RulesDeleting IP Filter Rules Port ReferencePptp VPN UDP port Used for Reference For more information about ipfw Starting and Stopping NAT Service NAT ServiceTo start NAT service Viewing the NAT Status Overview Configuring NAT ServiceMonitoring NAT Service To configure NAT serviceFor more information about natd To view the NAT divert logPage VPN Service Point to Point Tunneling Protocol Pptp Authentication MethodVPN and Security Transport ProtocolsEnabling and Configuring L2TP Transport Protocol Before You Set Up VPN ServiceManaging VPN Service Starting or Stopping VPN ServiceTo enable L2TP Enabling and Configuring Pptp Transport ProtocolTo enable Pptp To set routing definitions Configuring Additional Network Settings for VPN ClientsConfiguring VPN Network Routing Definitions To configure addition network settingsViewing a VPN Status Overview Monitoring VPN ServiceSetting the Log Detail Level for VPN Service Setting the VPN Log Archive IntervalTo view client connections Viewing the VPN LogViewing VPN Client Connections To view the logPage How NTP Works NTP ServiceSetting Up NTP Service Using NTP on Your NetworkTo set up NTP service To configure NTP on clients Configuring NTP on ClientsPage IPv6 Support Notation IPv6 Enabled ServicesIPv6 Addresses in the Server Admin IPv6 AddressesIPv6 Addressing Model IPv6 Reserved AddressesIPv6 Address Types Where to Find More Information Glossary GlossaryGlossary Glossary Name server See DNS Domain Name System Search path See search policy UCE unsolicited commercial email See spam Glossary Page Index Dhcp VPN

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