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The most obvious place to start is with phone directories Many companies now sell libraries of local phone books on CD-ROM that can be used to dump into war-dialing scripts Many websites also provide a similar service as the Internet continues to become one big massive online library Once a main phone number has been identified, attackers may war-dial the entire exchange surrounding that number For example, if Acme Corp s main phone number is 555-555-1212, a war-dialing session will be set up to dial all 10,000 numbers within 555-555-XXXX Using four modems, this range can be dialed within a day or two by most war-dialing software, so granularity is not an issue Another potential tactic is to call the local telephone company and try to sweet talk corporate phone account information out of an unwary customer service rep This is a good way to learn of unpublished remote access or datacenter lines that are normally established under separate accounts with different prefixes Upon request of the account owner, many phone companies will not provide this information over the phone without a password, although they are notorious about not enforcing this rule across organizational boundaries Besides the phone book, corporate websites are fertile phone number hunting grounds Many companies caught up in the free flow of information on the Web will publish their entire phone directories on the Internet This is rarely a good idea unless a valid business reason can be closely associated with such giveaways Phone numbers can be found in more unlikely places on the Internet One of the most damaging places for information gathering has already been visited earlier in this book but deserves a revisit here The Internet name registration database found at http:// wwwarinnet will dispense primary administrative, technical, and billing contact information for a company s Internet presence via the WHOIS interface The following (sanitized) example of the output of a WHOIS search on acmecom shows the do s and don ts of publishing information with InterNIC:.

Registrant: Acme, Incorporated (ACME-DOM) Princeton Rd Hightstown, NJ 08520 US Domain Name: ACMECOM Administrative Contact: Smith, John (JS0000) jsmith@ACMECOM 555-555-5555 (FAX) 555-555-5556 Technical Contact, Zone Contact: ANS Hostmaster (AH-ORG) hostmaster@ANSNET (800)555-5555

address, as you would for a typical mailing If you include it, choose whether to include the country or region by selecting the Never Include The Country/Region In The Address option button, the Always Include The Country/Region In The Address option button, or the Only Include The Country/Region If Different Than option button The last option button is usually the best choice; when you select it, choose the country in the drop-down list

Not only do attackers now have a possible valid exchange to start dialing, but they also have a likely candidate name (John Smith) to masquerade as to the corporate help

check box if you want Word to apply country- or region-specific address conventions to the address (For example, some countries place the equivalent of the zip code before the city) 4 If elements in the address appear in the wrong order, you may need to change the eld matching Follow these steps:

Determining where mail is handled is a great starting place to locate the target organization s firewall network Often in a commercial environment, mail is handled on the same system as the firewall, or at least on the same network Therefore, we can use the host command to help harvest even more information:

CHAPTER 16:

[bash]$ host examplecom examplecom has address 19216817 examplecom mail is handled (pri=10) by mailexamplecom examplecom mail is handled (pri=20) by smtp-forwardexamplecom

list, or select (not matched) from the bottom of the drop-down list to indicate that there is no match for the item

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address information in the Insert Address Block dialog box accordingly 5 Click the OK button Word closes the Insert Address Block dialog box and inserts the address block in the document as an <<AddressBlock>> merge eld, as shown here

DNS information provides a plethora of data to attackers, so it is important to reduce the amount of information available to the Internet From a host-configuration perspective, you should restrict zone transfers to only authorized servers For modern versions of BIND, the allow-transfer directive in the namedconf file can be used to enforce the restriction To restrict zone transfers in Microsoft s DNS, you can use the Notify option (see http://wwwmicrosoftcom/technet/prodtechnol/windows2000serv/maintain/ optimize/c19w2kad mspx for more information) For other nameservers, you should consult the documentation to determine what steps are necessary to restrict or disable zone transfers On the network side, you could configure a firewall or packet-filtering router to deny all unauthorized inbound connections to TCP port 53 Because name lookup requests are UDP and zone transfer requests are TCP, this will effectively thwart a zone-transfer attempt However, this countermeasure is a violation of the RFC, which states that DNS queries greater than 512 bytes will be sent via TCP In most cases, DNS queries will easily fit within 512 bytes A better solution would be to implement cryptographic transaction signatures (TSIGs) to allow only trusted hosts to transfer zone information For a great primer on TSIG security in Bind 9, see http://wwwlinux-magcom/2001-11/bind9_01html Restricting zone transfers will increase the time necessary for attackers to probe for IP addresses and hostnames However, because name lookups are still allowed, attackers could manually perform reverse lookups against all IP addresses for a given net block Therefore, you should configure external nameservers to provide information only about systems directly connected to the Internet External nameservers should never be configured to divulge internal network information This may seem like a trivial point, but we have seen misconfigured nameservers that allowed us to pull back more than 16,000 internal IP addresses and associated hostnames Finally, we discourage the use of HINFO records As you will see in later chapters, you can identify the target system s operating system with fine precision However, HINFO records make it that much easier to programmatically cull potentially vulnerable systems.