Safeguard Against Random Password Hacks

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A great tool I ran across to protect your server from random password attacks which I have been receiving recently from China.

Fail2ban scans log files and bans IP addresses that make repeated, unsuccessful attempts to access the server and then it updates the IPtables rules to reject those IP addresses for a period of time which is defined by you. It can also be configured to notify you if once these events occur.

Its no high-end Intrusion Prevention System, but it does the job.

Fail2ban comes preconfigured to detect and block attacks to ports 22 (ssh), 25 (SMTP) and 80 (http). Instructions on installing on CentOS are detailed below as well as adding functionality for ProFTPD.

I love package management as opposed to compiling because its clean and easy to maintain, so we will need to subscribe to repositories to install Fail2ban.

* Update the system

yum update

* Install DAG’s GPG key

rpm –import http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt

* Verify the package you have downloaded

rpm -K rpmforge-release-0.3.6-1.el5.rf.*.rpm

Security warning: The rpmforge-release package imports GPG keys into your RPM database. As long as you have verified the package and trust Dag then it should be safe.

* Download and Install the package

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.3.6-1.el5.rf.i386.rpm
rpm -ivh rpmforge-release-0.3.6-1.el5.rf.*.rpm

This will add a yum repository config file and import the appropriate GPG keys. At this point, you can set the priority of the RPMForge repository, and also of the CentOS repositories if you have not done so yet.

* Test with this command:

yum check-update

* Update the system

yum update

* Install Fail2ban

yum install fail2ban

* Configure Fail2ban by editing and adding to /etc/fail2ban.conf

maxfailures = 3 (the default is 5)

ignoreip = 127.0.0.1 <the_server_IP> <network_you_want_excluded/24>

* Enable E-Mail Notification

[MAIL]
# Option:  enabled
# Notes.:  enable mail notification when banning an IP address.
# Values:  [true | false]  Default:  false
#
enabled = true

to = <your_email_address>

* Add ProFTPD functionality

[proftpd]
enabled = true
logfile = /var/log/secure
fwstart = iptables -N fail2ban-proftpd
iptables -I INPUT -p tcp –dport ftp -j fail2ban-proftpd
iptables -A fail2ban-proftpd -j RETURN
fwend = iptables -D INPUT -p tcp –dport ftp -j fail2ban-proftpd
iptables -F fail2ban-proftpd
iptables -X fail2ban-proftpd
fwcheck = iptables -L INPUT | grep -q fail2ban-proftpd
fwban = iptables -I fail2ban-proftpd 1 -s <ip> -j DROP
fwunban = iptables -D fail2ban-proftpd -s <ip> -j DROP
timeregex = \S{3}\s{1,2}\d{1,2} \d{2}:\d{2}:\d{2}
timepattern = %%b %%d %%H:%%M:%%S
failregex = Maximum login attempts|no such user found|Failed password

* Set it to startup automatically with the system

chkconfig –levels 235 fail2ban on

* Start Fail2ban and walk away

/etc/init.d/fail2ban start

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Finding a Needle in a Haystack

I am going to go out on a limb and assert that over 80% of IT shops do not take security seriously and even those who do are not proactive about it.

Whenever an anomaly hits the network, system admins and network engineers hit the logs in an attempt to figure what is going on.

Ideally you will have a centralized server running “syslog” gathering logs from all devices on the network that can put out logs.

Unfortunately, unless you’re “Neo” from the movie “Matrix” it will almost impossible to make sense, interpret or pick up patterns from the vast amount of data in these logs.

This is were a good Log Analyzer comes in. There are well known log analyzers out there for web traffic, including AWStats, Analog, WebLogExpert, Webalizer and WebTrends but something more comprehensive is needed when it comes to security.

Unmatched as a security log analysis tool, “Splunk” gathers data from traps, alerts, syslog and snmp as well as imported logs  and lets you graph and search it via a simple web interface. In addition to helping find threats and dangerous trends, it can generate nice reports of your findings.

On the commercial front Sawmill looks like a good product, but I will need to demo and review it.

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Step by Step In Dealing With Conficker

This will turn out to be a “trojan horse” literally if actions are not taken to prevent it from spreading within the corporate network.

Below are step by step instructions on mitigating the risk of the threat that “Conficker”/”Downandup” poses.

Symptoms

============

Symptoms to help you determine if you are infected

  • Account lockout policies are being tripped
  • Automatic Updates, Background Intelligent Transfer Service, Windows Defender and Error Reporting Server Services are disabled
  • Errors related to SVCHOST
  • Domain Controllers are slow to respond to client requests
  • Network congestion
  • Various security related websites are not accessible including Windows Update.

For further details see the Microsoft Malware Protection Center write up for Win32/Conficker.b. or the Sekiur writeup here.

Solution

=========

Ideally you want to not only automate the removal of the “Conficker”/”Downandup” worm from a large number of computers but also take steps to minimize the risk of them being infected again.

The following script will attempt to remove the “Conficker”/”Downandup” worm and prevent further infection by taking the following steps:

  1. Install patch KB958644 for MS08-067 if not installed
  2. Attempt to remove the “Conficker”/”Downandup” worm
  3. Enable Hidden Setting
  4. Delete all scheduled tasks
  5. Stop and disable services. (lanmanserver, schedule)
  6. Run MSRT – Malicious Software Removal Tool
  7. Install Autorun hotfix if not installed
  8. Install KB950582 for vulnerability MS08-038
  9. Re-enable TCP Receive Window Auto-tuning on Windows Vista and Windows Server 2008
  10. Remove Hidden Setting
  11. Enable Automatic Updates, Background Intelligent Transfer and Error Reporting Services
  12. Restart
  13. Install patch KB958644 for MS08-067 and restart

You will need to download the following files and batch script and drop them into the NetLogon share.

  • Getver.exe – contained in ConfickerClean-v10.3.zip here ==>  and script to remove “Conficker”/”Downandup” locally here ==> .
  • SC.EXE – contained in ConfickerClean-v10.3.zip
  • REG.exe – contained in ConfickerClean-v10.3.zip
  • windows-kb890830-v2.6.exe – x86 version of MSRT, available here.
  • windows-kb890830-x64-v2.6.exe – x64 version of MSRT, available here.
  • sleep.exe – contained in ConfickerClean-v10.3.zip
  • Hotfix update for Windows 2000, Windows XP and Windows 2003, download all updates listed in http://support.microsoft.com/kb/953252, except the Itanium update as this script does not support Itanium.
  • Place all 3 updates in the Netlogon directory.
  • Security update MS08-038 for Windows Vista and Windows Server 2008 – http://www.microsoft.com/technet/security/Bulletin/MS08-038.mspx
    This vulnerability is not being exploited, however, to disable Autorun properly this needs to be applied as it contains a fix related to autorun, same as the one listed above in KB953252.

Now you will proceed to create and push a Group Policy to the domain.

  1. Edit the <domain.com> values in the script.
  2. Rename it to .BAT and drop it in the \\%windir%\sysvol\sysvol\\scriptsfolder (aka, Netlogon share).
  3. Create a Startup Script policy and reference this batch file. This needs to be a Startup Script and not a Logon script, so that the script runs under the machine account.
  4. Link the GPO with the Startup Script to the OU and Groups where you want it to apply.

Note:

Its not recommend you use this on DC’s or critical servers, those should be cleaned manually so that the services disabled below do not need to be left disabled for an extended period of time.

FAQ:

Why disable the Server service?

This is due to Weak Passwords which the malware attempts to exploit. The password change will need to be accomplished via password policy for the domain, resetting any local and domain admin password to a complex password which includes at least 10 characters and contains, alpha-numeric characters and extended characters such as a question mark or exclamation point.

Why disable the Task Scheduler service?

This is because the malware creates several AT jobs that run every hour to reinfect the system.

Why install MS08-067?

This is the main attack vector of the malware.

Why disable Autorun?

This is because the malware drops a binary file called Autorun.inf on all removable drives.

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Sources:

All credit to Microsoft Support Engineering

Worm Uses Social Engineering

A new worm has hit the Internet and its taking its toll on computers worldwide. It has been reported that over 9 million computers have already been infected.

The worm called “Downandup”, “Conficker” or “Kido” by different anti-virus vendors uses the Microsoft vulnerability which I blogged about here (Worm Takes Advantage Of Microsoft Flaw) and here (Microsoft Releases Emergency Patch).

The worm mostly spreads across networks, turning off the system restore and deleting the restore points, blocks access to security website, download additional malware from the author, attempts to infect other computers by scanning network shares and scheduled a task to re-infect the computer if removed.

What is interesting is that it can also spread by USB memory keys or devices making use of social engineering which makes it more dangerous to the untrained eye. When a USB drive is inserted it shows a modified AutoPlay screen seen below which will install the worm when the users inadvertently clicks on it.

According to SANS Internet Storm Center, one of the reasons the worm is infecting so many machines is that “Conficker” uses multiple infection vectors:

  1. It exploits the MS08-067 vulnerability,
  2. It brute forces Administrator passwords on local networks and spreads through ADMIN$ shares and finally
  3. It infects removable devices and network shares by creating a special autorun.inf file and dropping its own DLL on the device.

Characteristics –

When executed, the worm copies itself using a random name to the %Sysdir% folder.

(Where %Sysdir% is the Windows system folder; e.g. C:\Windows\System32)

It modifies the following registry key to create a randomly-named service on the affected syetem:

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{random}\Parameters\”ServiceDll” = “Path to worm”
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{random}\”ImagePath” = %SystemRoot%\system32\svchost.exe -k netsvcs

Attempts connections to one or more of the following websites to obtain the public ip address of the affected computer.

  • hxxp://www.getmyip.org
  • hxxp://getmyip.co.uk
  • hxxp://checkip.dyndns.org
  • hxxp://whatsmyipaddress.com

Attempts to download a malware file from the remote website: (Rogue Russian site is up but not serving file anymore)

  • hxxp://trafficconverter.biz/[Removed]antispyware/[Removed].exe

Starts a HTTP server on a random port on the infected machine to host a copy of the worm.

Continuously scans the subnet of the infected host for vulnerable machines and executes the exploit. If the exploit is successful, the remote computer will then connect back to the http server and download a copy of the worm.

Later variants of w32/Conficker.worm are using scheduled tasks and Autorun.inf file to replicate on to non vulnerable systems or to reinfect previously infected systems after they have been cleaned.

Suggestions –

  1. Disable AutoPlay in your environment.
  2. Run a good security suite.
  3. Keep your computer updated with the latest patches.
  4. Be PROACTIVE and look for the worm in your environment.

Sources:

http://www.nai.com
http://www.symantec.com
http://www.f-secure.com
http://isc.sans.org

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