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# Detecting Remcos for Volatility
#
# LICENSE
# Please refer to the LICENSE.txt in the https://github.com/JPCERTCC/MalConfScan/
#
# How to use:
# 1. cd "Volatility Folder"
# 2. mv remcosscan.py volatility/plugins/malware
# 3. python vol.py remcosconfig -f images.mem --profile=Win7SP1x64
import volatility.plugins.taskmods as taskmods
import volatility.win32.tasks as tasks
import volatility.utils as utils
import volatility.debug as debug
import volatility.plugins.malware.malfind as malfind
import re
import pefile
from struct import unpack, unpack_from
from socket import inet_ntoa
from collections import OrderedDict
try:
import yara
has_yara = True
except ImportError:
has_yara = False
remcos_sig = {
'namespace1' : 'rule Remcos { \
strings: \
$remcos = "Remcos" ascii fullword \
$url1 = "Breaking-Security.Net" ascii fullword \
$url2 = "BreakingSecurity.Net" ascii fullword \
$resource = "SETTINGS" ascii wide fullword \
condition: 1 of ($url*) and $remcos and $resource}'
}
# MZ Header
MZ_HEADER = b"\x4D\x5A\x90\x00"
# Resource pattern
RESOURCE_PATTERNS = [re.compile("\xE0\x00\x00\x07\xE0\x00\x00\x07\xFF\xFF\xFF\xFF", re.DOTALL)]
# Flag
FLAG = {"\x00": "Disable", "\x01": "Enable"}
idx_list = {
0: "Host:Port:Password",
1: "Assigned name",
2: "Connect interval",
3: "Install flag",
4: "Setup HKCU\\Run",
5: "Setup HKLM\\Run",
6: "Setup HKLM\\Explorer\\Run",
7: "Setup HKLM\\Winlogon\\Shell",
8: "Setup HKLM\\Winlogon\\Userinit",
9: "Install path",
10: "Copy file",
11: "Startup value",
12: "Hide file",
13: "Unknown13",
14: "Mutex",
15: "Keylog flag",
16: "Keylog path",
17: "Keylog file",
18: "Keylog crypt",
19: "Hide keylog file",
20: "Screenshot flag",
21: "Screenshot time",
22: "Take Screenshot option",
23: "Take screenshot title",
24: "Take screenshot time",
25: "Screenshot path",
26: "Screenshot file",
27: "Screenshot crypt",
28: "Mouse option",
29: "Unknown29",
30: "Delete file",
31: "Unknown31",
32: "Unknown32",
33: "Unknown33",
34: "Unknown34",
35: "Unknown35",
36: "Audio record time",
37: "Audio path",
38: "Audio folder",
39: "Unknown39",
40: "Unknown40",
41: "Connect delay",
42: "Unknown42",
43: "Unknown43",
44: "Unknown44",
45: "Unknown45",
46: "Unknown46",
47: "Unknown47",
48: "Copy folder",
49: "Keylog folder",
50: "Unknown50",
51: "Unknown51",
52: "Unknown52",
53: "Unknown53",
54: "Keylog file max size",
55: "Unknown55",
}
setup_list = {
0: "Temp",
2: "Root",
3: "Windows",
4: "System32",
5: "Program Files",
6: "AppData",
7: "User Profile",
8: "Application path",
}
class remcosConfig(taskmods.DllList):
"""Parse the Remcos configuration"""
@staticmethod
def is_valid_profile(profile):
return (profile.metadata.get('os', 'unknown') == 'windows'), profile.metadata.get('memory_model', '32bit')
def get_vad_base(self, task, address):
for vad in task.VadRoot.traverse():
if address >= vad.Start and address < vad.End:
return vad.Start, vad.End
return None
# RC4
def rc4(self, data, key):
x = 0
box = range(256)
for i in range(256):
x = (x + box[i] + ord(key[i % len(key)])) % 256
box[i], box[x] = box[x], box[i]
x = 0
y = 0
out = []
for char in data:
x = (x + 1) % 256
y = (y + box[x]) % 256
box[x], box[y] = box[y], box[x]
out.append(chr(ord(char) ^ box[(box[x] + box[y]) % 256]))
return ''.join(out)
def parse_config(self, data):
p_data = OrderedDict()
key_len = ord(data[0])
key = data[1:key_len + 1]
enc_data = data[key_len + 1:]
config = self.rc4(enc_data, key)
#configs = config.split("@@")
configs = re.split("\x1E|@@", config)
for i, cont in enumerate(configs):
if cont == "\x00" or cont == "\x01":
p_data[idx_list[i]] = FLAG[cont]
else:
if i in [9, 16, 25, 37]:
p_data[idx_list[i]] = setup_list[int(cont)]
else:
p_data[idx_list[i]] = cont
return p_data
def calculate(self):
if not has_yara:
debug.error("Yara must be installed for this plugin")
addr_space = utils.load_as(self._config)
os, memory_model = self.is_valid_profile(addr_space.profile)
if not os:
debug.error("This command does not support the selected profile.")
rules = yara.compile(sources=remcos_sig)
for task in self.filter_tasks(tasks.pslist(addr_space)):
scanner = malfind.VadYaraScanner(task=task, rules=rules)
for hit, address in scanner.scan():
vad_base_addr, end = self.get_vad_base(task, address)
proc_addr_space = task.get_process_address_space()
data = proc_addr_space.zread(vad_base_addr, end - vad_base_addr)
config_data = []
# resource PE search
dll_index = data.rfind(MZ_HEADER)
dll_data = data[dll_index:]
try:
pe = pefile.PE(data=dll_data)
except:
outfd.write("[!] Can't mapped PE.\n")
continue
rc_data = ""
for idx in pe.DIRECTORY_ENTRY_RESOURCE.entries:
for entry in idx.directory.entries:
if str(entry.name) in "SETTINGS":
try:
data_rva = entry.directory.entries[0].data.struct.OffsetToData
size = entry.directory.entries[0].data.struct.Size
rc_data = dll_data[data_rva:data_rva + size]
print("[*] Found SETTINGS resource.")
except:
debug.error("Faild to load SETTINGS resource.")
if not len(rc_data):
for pattern in RESOURCE_PATTERNS:
mc = re.search(pattern, dll_data)
if mc:
try:
config_end = mc.end() + 1
while dll_data[config_end:config_end + 2] != "\x00\x00":
config_end += 1
rc_data = dll_data[mc.end():config_end - 1]
except:
debug.error("Remcos resource not found.")
config_data.append(self.parse_config(rc_data))
yield task, vad_base_addr, end, hit, memory_model, config_data
break
def render_text(self, outfd, data):
delim = '-' * 70
for task, start, end, malname, memory_model, config_data in data:
outfd.write("{0}\n".format(delim))
outfd.write("Process: {0} ({1})\n\n".format(task.ImageFileName, task.UniqueProcessId))
outfd.write("[Config Info]\n")
for p_data in config_data:
for id, param in p_data.items():
outfd.write("{0:<16}: {1}\n".format(id, param))
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