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IoT
6/26/2019
05:30 PM
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New Linux Worm Attacks IoT Devices

Silex has 'bricked' more than 2,000 Linux-based IoT devices so far.

A new Internet of Things (IoT) bricking worm — malware designed to permanently disable the hardware it infects — is hitting Linux-based devices, and it appears the culprit responsible for the attack is 14 years old. 

The new software, dubbed "Silex," is running across the Internet looking for Linux systems deployed with default admin credentials. Once it finds such a system, it overwrites all of the system's storage with random data, drops its firewall rules, removes its network configuration, and then restarts the system — effectively rendering the device useless.

Discovered by Larry Cashdollar, a vulnerability researcher and member of Akamai's Security Incident Response Team, the software is purely destructive; it captures no data and asks for no ransom. Researcher Ankit Anubhav traced the malware back to its origins and found the developer, who uses the online name "Light Leafon." According to Anubhav, the malware's author says that additional destructive capabilities are planned for future Silex variants.

More than 2,000 systems have already been damaged by Silex, which is not technically limited to IoT devices. It could attack any Linux system deployed on the Internet with open telnet ports and default admin credentials. Other researchers have noted that the command-and-control servers for Silex have IP addresses linked to Iran, leading some to speculate that political, as well as simply destructive, aims are behind its release.

Read more herehere, and here.

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tdsan
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tdsan,
User Rank: Ninja
6/27/2019 | 2:52:55 PM
Linux Worm Exploits and Defenses
The new software, dubbed "Silex," is running across the Internet looking for Linux systems deployed with default admin credentials. Once it finds such a system, it overwrites all of the system's storage with random data, drops its firewall rules, removes its network configuration, and then restarts the system — effectively rendering the device useless.

I do agree the responsibility should rest with the consumer where the system asks or provides insight on how to change the admin password but this should be a mandatory function (to change the password and remove telnet or disable it) when the user logs in. A number of companies are doing this but after reading the report, it seems this practice is not performed across the board.

 
It could attack any Linux system deployed on the Internet with open telnet ports and default admin credentials.

Ways to thwart the linux attack:
  • iptables -I INPUT 1 -m multiport --dport 23 -s 0.0.0.0/0 -m conntrack --ctstate NEW,ESTABLISHED,RELATED -j DROP (the code can be updated to include more ports (-m option), conntrack tracks the attempts and the --ctstate looks for NEW, ESTABLISHED and Relates sessions, the -J is used to drop the connection)
  • ufw deny in -proto tcp from 0.0.0.0/0 to 0.0.0.0/0 port 23 "comment Deny telnet access" or a shorter method is ufw deny in telnet.
  • Firewall - disable telnet from the IOT device or only allow internal access when needed if telnet is essential to diagnostic issues
  • Another option would be to stop the service all together
service stop telnet-server or systemctl stop telnet-server

 

Shodan provides a complete list of devices that still have default passwords enabled.

 Todd

 
Webtoolsoffers
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Webtoolsoffers,
User Rank: Apprentice
6/28/2019 | 4:31:00 AM
Re: Linux Worm Exploits and Defenses
The IoT devices related to the internet. Now-a-day IoT devices is most useful because we can get information through mobile interenet
Dr.T
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Dr.T,
User Rank: Ninja
6/28/2019 | 6:46:12 PM
Re: Linux Worm Exploits and Defenses
The IoT devices related to the internet. That is why they become vulnerable too.
Dr.T
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Dr.T,
User Rank: Ninja
6/28/2019 | 6:42:14 PM
Re: Linux Worm Exploits and Defenses
I do agree the responsibility should rest with the consumer where the system asks or provides insight on how to change the admin password Anting left to consumers will be at high risk. Better to avoid expecting anything from consumers.
tdsan
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tdsan,
User Rank: Ninja
6/28/2019 | 7:40:48 PM
Re: Linux Worm Exploits and Defenses
Yes, I agree, that is why I had mentioned in my excert that the vendor should disable telnet altogether or block it.

In addition, companies like Cisco and Juniper ask the user to change the default password. If the user does not change the password then the system should be halted until they change it based on recommended security guidelines (listed below).

NIST password guidelines - "NIST guidance recommends the following for passwords: An eight character minimum and 64 character maximum length. The ability to use all special characters but no special requirement to use them."
  • An eight character minimum and 64 character maximum length
  • The ability to use all special characters but no special requirement to use them
  • Restrict sequential and repetitive characters (e.g. 12345 or aaaaaa)
  • Restrict context specific passwords (e.g. the name of the site, etc.)
  • Restrict commonly used passwords (e.g. [email protected], etc.)
  • Restrict passwords obtained from previous breach corpuses
NIST Security Password Guidelines

Todd

 
Dr.T
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Dr.T,
User Rank: Ninja
6/28/2019 | 6:44:13 PM
Re: Linux Worm Exploits and Defenses
A number of companies are doing this but after reading the report, it seems this practice is not performed across the board. Most SME would not pay enough attention to it so they mostly miss it.
Dr.T
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Dr.T,
User Rank: Ninja
6/28/2019 | 6:40:46 PM
For fun
the software is purely destructive; it captures no data and asks for no ransom. Researcher Ankit Anubhav traced the malware back to its origins and found the developer, who uses the online name "Light Leafon." Obviously this was for fun. Distraction is huge.
tdsan
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tdsan,
User Rank: Ninja
6/28/2019 | 8:46:28 PM
Re: For fun
"the software is purely destructive; it captures no data and asks for no ransom. Researcher Ankit Anubhav traced the malware back to its origins and found the developer, who uses the online name "Light Leafon." " Obviously this was for fun. Distraction is huge.

I am not so sure it was all for fun, I think it was also being used to test its capability for another purpose. Think about this, if the actor could access systems with default passwords, then what about writing a hash algorithm to run a for loop to check for possible password combinations.
  1. Check to see if they can get to the device and apply a default username and password
  2. Create a payload or add a function statement that goes through a list of passwords

I think this is a logical step in their next attempt but again we are theorizing, only time will tell.
import getpass
import sys
import telnetlib
import time

#Getting the user information
user=input("Enter User name: ")
password=getpass.getpass()

#open file
iplist=open("ipfile.txt")

#Loop through IP address and execute commands
for line in  iplist:

 Host=line.strip("\n")    
 print ("Configuring Switch",Host)
 tn = telnetlib.Telnet(Host)    
 tn.read_until(b"Username: ")   
 tn.write(user.encode('ascii') + b"\n")
 tn.read_until(b"Password: ")
 tn.write(password.encode('ascii')+b"\n")
 time.sleep(2)     
 tn.write(b"enable\n")  
 time.sleep(2)
 tn.write(b"admin\n")  
 time.sleep(2)
 tn.write(b"config t\n")
 time.sleep(2)
 tn.write(b"snmp-server community Secured ro\n") 
 print ("Switch ",Host,"Configured")
 line=tn.read_some()
 tn.close()                           
 print (line)                      

#closing file 
ipfile.close()

 Todd
Dr.T
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Dr.T,
User Rank: Ninja
6/28/2019 | 6:47:51 PM
Defaults
It could attack any Linux system deployed on the Internet with open telnet ports and default admin credentials. So it is not supposed to be an attack at all. Who would leave defaults as they are today?
RyanSepe
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RyanSepe,
User Rank: Ninja
6/29/2019 | 8:16:53 PM
Re: Defaults
Definitely concur here. But obviously there are still those out there who are foolish enough for this to still be effective. :( Its quite sad.
tdsan
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tdsan,
User Rank: Ninja
6/29/2019 | 8:34:21 PM
Re: Defaults
RyanSepe
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RyanSepe,
User Rank: Ninja
6/30/2019 | 9:02:42 AM
Re: Defaults
That's depressing.
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