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The Berkeley Internet Name Domain (BIND) package is the most widely used an implementation of Domain Name Service (DNS) -- the critical means by which we all locate systems on the Internet by name (e.g., www.sans.org) without having to know specific IP addresses -- and this makes it a favorite target for attack. Sadly, according to a mid-1999 survey, about 50% of all DNS servers connected to the Internet are running vulnerable versions of BIND. 

Most web servers support Common Gateway Interface (CGI) programs to provide interactivity in web pages, such as data collection and verification. Many web servers come with sample CGI programs installed by default. Unfortunately, many CGI programmers fail to consider ways in which their programs may be misused or subverted to execute malicious commands. Vulnerable CGI programs present a particularly attractive target to intruders because they are relatively easy to locate, and they operate with the privileges and power of the web server software itself. Intruders are known to have exploited vulnerable CGI programs to vandalize web pages, steal credit card information, and set up back doors to enable future intrusions, even if the CGI programs are secured.

3. Remote Procedure Call (RPC) weaknesses in rpc.ttdbserverd (ToolTalk), rpc.cmsd (Calendar Manager), and rpc.statd that allow immediate root compromise

Remote procedure calls (RPC) allow programs on one computer to execute programs on a second computer. They are widely-used to access network services such as shared files in NFS. Multiple vulnerabilities caused by flaws in RPC, are being actively exploited. There is compelling evidence that the vast majority of the distributed denial of service attacks launched during 1999 and early 2000 were executed by systems that had been victimized because they had the RPC vulnerabilities. The broadly successful attack on U.S. military systems during the Solar Sunrise incident also exploited an RPC flaw found on hundreds of Department of Defense systems.

4. RDS security hole in the Microsoft Internet Information Server (IIS)

Microsoft’s Internet Information Server (IIS) is the web server software found on most web sites deployed on Microsoft Windows NT and Windows 2000 servers. Programming flaws in IIS’s Remote Data Services (RDS) are being employed by malicious users to run remote commands with administrator privileges. Some participants who developed the "Top Ten" list believe that exploits of other IIS flaws, such as .HTR files, are at least as common as exploits of RDS. Prudence dictates that organizations using IIS install patches or upgrades to correct all known IIS security flaws when they install patches or upgrades to fix the RDS flaw.

5. Sendmail and MIME buffer overflows as well as pipe attacks that allow immediate root compromise.

Sendmail is the program that sends, receives, and forwards most electronic mail processed on UNIX and Linux computers. Sendmail’s widespread use on the Internet makes it a prime target of attackers. Several flaws have been found over the years. The very first advisory issued by CERT/CC in 1988 made reference to an exploitable weakness in sendmail. In one of the most common exploits, the attacker sends a crafted mail message to the machine running Sendmail, and Sendmail reads the message as instructions requiring the victim machine to send its password file to the attacker’s machine (or to another victim) where the passwords can be cracked.

6. sadmind and mountd

Sadmind allows remote administration access to Solaris systems, providing graphical access to system administration functions. Mountd controls and arbitrates access to NFS mounts on UNIX hosts. Buffer overflows in these applications can be exploited allowing attackers to gain control with root access

7.Global file sharing and inappropriate information sharing via NetBIOS and Windows NT ports 135->139 (445 in Windows2000), or UNIX NFS exports on port 2049, or Macintosh Web sharing or AppleShare/IP on ports 80, 427, and 548.

This is very important information for home networks. These services allow file sharing over networks. When improperly configured, they can expose critical system files or give full file system access to any hostile party connected to the network. Many computer owners and administrators use these services to make their file systems readable and writeable in an effort to improve the convenience of data access. Administrators of a government computer site used for software development for mission planning made their files world readable so people at a different government facility could get easy access. Within two days, other people had discovered the open file shares and stolen the mission planning software.

When file sharing is enabled on Windows machines they become vulnerable to both information theft and certain types of quick-moving viruses. A recently released virus called the 911 Worm uses file shares on Windows 95 and 98 systems to propagate and causes the victim’s computer to dial 911 on its modem. Macintosh computers are also vulnerable to file sharing exploits.

The same NetBIOS mechanisms that permit Windows File Sharing may also be used to enumerate sensitive system information from NT systems. User and Group information (usernames, last logon dates, password policy, RAS information), system information, and certain Registry keys may be accessed via a "null session" connection to the NetBIOS Session Service. This information is typically used to mount a password guessing or brute force password attack against the NT target.

8. User IDs, especially root/administrator with no passwords or weak passwords.

Some systems come with "demo" or "guest" accounts with no passwords or with widely-known default passwords. Service workers often leave maintenance accounts with no passwords, and some database management systems install administration accounts with default passwords. In addition, busy system administrators often select system passwords that are easily guessable ("love," "money," "wizard" are common) or just use a blank password. Default passwords provide effortless access for attackers. Many attackers try default passwords and then try to guess passwords before resorting to more sophisticated methods. Compromised user accounts get the attackers inside the firewall and inside the target machine. Once inside, most attackers can use widely-accessible exploits to gain root or administrator access.

9. IMAP and POP buffer overflow vulnerabilities or incorrect configuration.

IMAP and POP are popular remote access mail protocols, allowing users to access their e-mail accounts from internal and external networks. The "open access" nature of these services makes them especially vulnerable to exploitation because openings are frequently left in firewalls to allow for external e-mail access. Attackers who exploit flaws in IMAP or POP often gain instant root-level control.

10. Default SNMP community strings set to ‘public’ and ‘private.’

The Simple Network Management Protocol (SNMP) is widely used by network administrators to monitor and administer all types of network-connected devices ranging from routers to printers to computers. SNMP uses an unencrypted "community string" as its only authentication mechanism. Lack of encryption is bad enough, but the default community string used by the vast majority of SNMP devices is "public", with a few "clever" network equipment vendors changing the string to "private". Attackers can use this vulnerability in SNMP to reconfigure or shut down devices remotely. Sniffed SNMP traffic can reveal a great deal about the structure of your network, as well as the systems and devices attached to it. Intruders use such information to pick targets and plan attacks.

Additional Threat: A High Priority Bonus Item for Windows Users and Administrators:
Various Scripting Holes in Internet Explorer and Office2000

Recent virus attacks have illustrated how macro and script code could spread easily through e-mail attachments, and people were admonished to avoid opening potentially dangerous attachments. However, Windows users can also spread malicious viruses without opening attachments. Microsoft Outlook and Outlook Express will execute HTML and script code in an e-mail in their default installations. In addition, several so-called ActiveX components are incorrectly executable from an e-mail containing HTML and script code. Some of the vulnerable controls include the Scriplet.typlib (ships with IE 4.x and 5.x) and the UA control (Office 2000). Other vulnerabilities arising from the use of Active Scripting are that an e-mail could be used to install new software on a users computer.

A relatively benign virus known as the kak worm is already spreading through these mechanisms. A malicious version of kak can be anticipated at any time. We recommend that all users and administrators set Outlook and Outlook Express to read e-mail in the "Restricted Sites Zone" and then further disable all Active Scripting and ActiveX related settings in that zone. This is done in the Options dialog's Security tab, but can be automated using System Policies. Microsoft has made patches available for the individual problems and is readying a patch which will set the security settings in Outlook, but apparently has no plans on fixing Outlook Express.

Some Valuable Tips:

An important element to remember when securing your information is the importance of strong passwords. Always try to use a combination of uppercase and lowercase letters as well as numbers and other extended characters -- just be sure that you pick something that is memorable.  Syllables work well; e.g., "gola3bonu" or "uwitga9hoolor." Always pick a password with at least 8 characters.

Use a secure screen saver even at home and set it for a reasonable period delay -- say, 15 minutes.  If it gets in your way, extend the delay.

Encrypt the sensitive files on your system.

Don’t forget to protect access to your printer -- you don’t want some prankster printing junk (or worse) on your paper.

Note: The information presented in this article was gathered from various sources as well as some original work as well. The following sources were used: SecurityPortal and The SANS Organization.