Enumeratingslides (c) 2012 by Richard Newman

based on Hacking Exposed 7 by McClure, Scambray, and Kurtz

What is Enumeration?How does it differ from footprinting and scanning?

– Footprinting did not necessarily attempt to access the target system(s) directly

– Scanning involved transient contact– Enumeration involves establishing connections and directed

queries

Information typically gathered– User account names (for password attacks)– Misconfigured shared resources– Software version and patch state (for known vulnerabilities)

Detailed examination of target systems

Platform specific – how you interact depends on target service/system

Service Fingerprinting

Automated method– Easy to use, use likely to increase– Generates a lot of traffic – likely to be noticed– Takes significant time

Nmap Version Scanning– Popularity=9; Simplicity=8; Impact=3; Risk Rating=7– Use -sV switch– Can find “hidden” services (use same port as other service)

Amap Version Scanning (thc.org/thc-amap/)– Popularity=9; Simplicity=8; Impact=3; Risk Rating=7– Older than nmap– Uses different patterns, so gives a second opinion

Vulnerability Scanners - 1Automated VS tools – Use when stealth not required

– Know defender is not monitoring– Moving too fast to care

Countermeasures– Keep system patched– Do your own scans – IDS – detect (pretty noisy)– IPS – prevent (slow down attacks to discourage, delay attacker)

Vulnerability Scanners - 2Nessus Scanning (nessus.org/products/nessus)

Popularity=9; Simplicity=9; Impact=6; Risk Rating=8– Easy to use GUI– Kept up to date– Optimized performance– Client ported to iPhone and Android– Extendable with user-developed custom plug-ins– Nessus Attack Scripting Language (NASL)– Open source version OpenVAS (openvas.org) is free

Vulnerability Scanners - 3Nmap Scanning Engine (NSE) Scanning

Popularity=7; Simplicity=6; Impact=5; Risk Rating=6– Extendable with user-developed scripts– Lua interpreted language– Intended for specific probing– - - script or -sC options to run scripts

Basic Banner GrabbingPopularity=5; Simplicity=9; Impact=1; Risk Rating=5

telnet – Ascii-based interactive session client– Can use to connect to many servers (ASCII-based)

netcat– “TCP/IP Swiss army knife”– Allows file input for tedious probes

Countermeasures– Shut down unnecessary services– Restrict access to services– Disable banner display (vendor dependent)– Do your own checks

Common Network Services - 1- FTP- Telnet- SMTP- DNS- TFTP- Finger- HTTP- MSRPC- NetBIOS Name Service- SMB Null Session

Common Network Services - 2- SNMP- BGP- Active Directory LDAP- Unix RPC- rwho, rusers- NIS- SQL Resolution Service- Oracle TNS- NFS- IPSec/IKE

FTP EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

- File Transfer Protocol – TCP port 21– Less used now– Allows upload of (malicious) files– Often allows anonymous access using any email address– Get banner– Determine access

- Countermeasures– Turn off – Secure FTP (SFTP) uses SSH– FTP Secure (FTPS) uses SSL– HTTP for public information access

Telnet EnumerationPopularity=4; Simplicity=9; Impact=3; Risk Rating=5

Telnet TCP 23– Used for remote access– Transmits data in cleartext– Often displays host system info– Even if it doesn't, the prompt may reveal system– May be used for attacking accounts if lockout not used– May reveal valid usernames from login attempts

Countermeasures– Turn off– Use secure shell (SSH) instead– Modify banner messages– Modify error messages– Account locking/drop connection on login failure

SMTP EnumerationPopularity=5; Simplicity=9; Impact=1; Risk Rating=5

Simple Mail Transport Protocol – TCP 25– Used universally for email transfer– ASCII protocol for requests/replies– VRFY – verify user names – EXPN – provide actual delivery email address of alias– vrfy.pl script allows a file containing a list of user names to

be tested and valid user names reported

Countermeasures– Configure to turn off VRFY and EXPN, or– Configure to require authentication/privileges to use them

DNS Enumeration - 1Popularity=5; Simplicity=9; Impact=2; Risk Rating=5

Domain Name Service (DNS) – TCP/UDP 53– Used for footprinting already– UDP used for most interactions– TCP for zone transfers– Zone transfer dumps entire contents of zone files

• HINFO, hostname-IP mappings

– SRV records allow search by service type– Nslookup, dig to access– BIND (Berkeley Internet Name Domain) enumeration

• Reveals BIND version

• Often allows zone transfer

DNS Enumeration - 2Domain Name Service (DNS)

– DNS Cache snooping

• DNS servers cache responses to recent queries

• Attacker can force server to only use cache– +norecurse option in dig

• Find recent accesses (or not) to particular FQDN

• Answer flag set to 0 if not, 1 if recent access– Automated DNS Enumeration

• Dnsenum (code.google.com/p/dnsenum/)

• Fierce.pl (ha.ckers.org/fierce)

• Web services for same (e.g., centralops.net)

Countermeasures– Two DNS servers – one for public, one for private use– Block DNS zone transfers except to authorized hosts– Block version.bind requests– Disable DNS cache-snooping

TFTP EnumerationPopularity=1; Simplicity=3; Impact=7; Risk Rating=3

Trivial FTP (TFTP) – TCP/UDP 69– Quick-and-dirty FTP– Cleartext, no authentication– Requires knowledge of file name (exactly)– May allow download of sensitive file (e.g., /etc/passwd,

/etc/shadow, network device configuration files, etc.)

Countermeasures– Turn off, if possible– Wrap in TCP wrapper to restrict access– Limit access to /tftpboot/ directory– Block at border firewall

Finger EnumerationPopularity=7; Simplicity=10; Impact=1; Risk Rating=6

Finger – TCP/UDP 79– Reveals logged-in users, idle times– User info given from public file info

Countermeasures– Turn off– Block port 79– Restrict access– Restrict info given

HTTP EnumerationPopularity=5; Simplicity=9; Impact=1; Risk Rating=5

Hypertext Transfer Protocol (HTTP) – TCP 80– Get type and version of web server– HEAD can get banner info

• But so popular with worms it can trigger IDS

– If server uses SSL, use openssl or sll proxy to connect– Can download all web pages for offline search

• Grendel-scan

• Robots.txt file for “do not search” regions....

Countermeasures– Change banner– Microsoft IIS lockdown tool

MSRPC EnumerationPopularity=7; Simplicity=8; Impact=1; Risk Rating=5

Microsoft Remote Procedure Call (MSRPC) – TCP 135– RPC portmapper for windows– Gives list of services with version and IP/protocol/port info– Winfingerprint tool (sourceforge)– See hsc.fr/ressources/articles/win_net_srv

Countermeasures– Restrict outside access– Require use of VPN for external access– Use OWA (Outlook Web Access) for remote mail access

NBNS EnumerationPopularity=7; Simplicity=5; Impact=3; Risk Rating=5

NetBIOS Name Service (NBNS) – UDP 137– Early windows version of DNS– net view command

• Usually only works on local LAN segment

• /domain for domains

• /domain:dname for hosts on specific domain (dname)

– nltest tool – identifies domain controllers (with auth creds)– netviewx tool – lists servers with specific services– nbstat, nbtscan – dump netbios name table, with users– nmbscan tool for Linux

Countermeasures– Restrict access on hosts, routers (test – may break apps)– Disable Alerter and Messenger Service on hosts

SMB Null Session EnumerationPopularity=8; Simplicity=10; Impact=8; Risk Rating=9

Server Message Block (SMB) Null Session – TCP 139/445– Windows NT and descendents – file and print sharing– Samba in Linux– Can give remote access to attacker– a.k.a. Red Button, anonymous login, null session connection

SMB Null Session (2)Establish “null session”

– C:\>net use \\192.168.202.33\IPC$ “” /u:“”– Similar to mount network drive command– Connects to hidden IPC share at given IP as built-in

anonymous user (/u:“”) with null password (“”)– Allows access to targeted host

Enumerating File Shares– C:\>net view \\host– Shows IP address and shares on remote systems– Srvcheck, srvinfo (microsoft.com/downloads/...)– DumpSec (nee DumpAcl) – SomarSoft.com– Wholesale approach – for sysadmin (not hacker)

• ShareEnum (SysInternal)

• Networkscanner (SoftPerfect)

SMB Null Session (3)Share Scanning wholesale for hackers

– Includes password brute-forcing (may be intelligent)– Legion– NetBIOS Auditing Tool (NAT) (see hackingexposed.com)

Registry Enumeration– Registry holds keys indicating applications installed– Also holds user info– and services– and holds configuration info (e.g., lockout number for failed

password attempts)– Also may hold pointers to back doors– All of which can suggest exploits

– Check if Registry is locked down using reg

SMB Null Session (4)Enumerating Trusted Domains

– Nltest /server:server_name /trusted_domains

User Enumeration– DumpSec

• List of users, groups, system policies, user rights– Following work with RestrictAnonymous=1, with null session– UserInfo/UserDump (hammerofgod.com)– GetAcct (securityFriday.com)– sid2user & user2sid (evgenii.rudnyi.ru/soft/sid/sid.txt)

• SID is security ID – variable length value set at install

• See also http://en.wikipedia.org/wiki/Security_Identifier

• User IDs (and much more) based on SID

SMB Null Session (5)SIDs

– C:\>user2sid \\targetIP “domain users”– Returns SID of host (hyphenated, S-1-...)– Digits following last hyphen is Relative ID (RID)– RID predefined for built-in users and groups

• 500=admin

• 501=guest– RID for users starts at 1000 for NT and increments

• RID not reused => can see users past and present

All-in-one tools– Cain & Abel (oxid.it/cain.html)– Winfingerprint (sourceforge.net) – also Active Directory, WMI– NBTEnum (try on packetstorm) – includes intelligent BF

attack– enum (BindView, Symantec). Enum4linux (Portcullis Security)– NetE (cult of the dead cow)– Winfo (ntsecurity.nu)

SMB Null Session (6)Popularity=8; Simplicity=10; Impact=8; Risk Rating=9

Countermeasures– Filter TCP/UDP ports 139 & 445 at perimeter– Self audit– Unbind WINS Client, or– Set RestrictAnonymous key (=0 is open, =1 can be

bypassed, =2 means no null sessions possible) in NT– More granular access control in later Windows versions– HKLM\System\CurrentControlSet\Control\SecurePipeServer\

Winreg and subkeys (e.g., AllowedPaths)

SNMP EnumerationPopularity=7; Simplicity=9; Impact=3; Risk Rating=6

Simple Network Management Protocol – UDP 161– “Security Not My Problem” - lacks strong protections– Password authentication – well-known default pw– Access to get and set MIBs (mgt info bases)– Vendor specific extensions to MIBs– Uses ASN.1 syntax for object IDs (OIDs)

SNMP Enumeration (2)

Tools– Snmputil, snmpget, snmpwalk commandline tools– Snmpget (linux/unix) in net-snmp suite at SourceForge– Copy-router-config.pl (muts)– IP Network Browser – GUI tool (solarwinds.com)

Targets– Running services– Share names– Share paths– Comments on shares– Usernames– Domain name– Architecture, OS version

SNMP Enumeration (3)SNMP Scanners

– Simple, light-weight => perfect for automated scanning– SNScan (mcafee.com/us/downloads/free-tools/snscan.aspx)

• Community and range to scan (or in file)

• Hostname and (MIB version of) OS version

• Csv file export– onesixtyone (portcullis-security.com/16.php)

• Command line version of SNScan

Countermeasures– Remove or disable SNMP agents on hosts– Use obscure community names (e.g., NOT “public” or

“private”)– Block port 161 at all perimeter network access devices– Restrict access to specific IP addresses– Use SNMPv3 (more secure)– Set Registry to permit only authorized access

BGP EnumerationPopularity=2; Simplicity=6; Impact=2; Risk Rating=3

Border Gateway Protocol (BGP) – TCP 179– Interdomain routing protocol– Determine Autonomous Systems Number (ASN) of target– Query routers to get all networks where AS Path ends with

desired ASN– Only uses IP addresses and ASNs

• Get ASN from whois search (if name known)

• Get ASN from router using IP address (if known)– Use telnet to router – show ASN path– Use last ASN on list as target ASN– May be false if BGP not used!!!

Countermeasures - none

Active Directory LDAP EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

Active Directory LDAP

Countermeasures

Unix RPC EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

Unix Remote Procedure Call (RPC)

Countermeasures

rwho, rusers EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

rwho, rusers

Countermeasures

NIS EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

NIS

Countermeasures

SQL Resolution Service Enumeration

Popularity=1; Simplicity=10; Impact=1; Risk Rating=4

SQL Resolution Service

Countermeasures

Oracle TNS EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

Oracle TNS

Countermeasures

NFS EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

NFS

Countermeasures

IPSec/IKE EnumerationPopularity=1; Simplicity=10; Impact=1; Risk Rating=4

IPSec/IKE

Countermeasures