The page may not load correctly.
An analysis of the technologies used by cybercriminals allows us to draw conclusions about the virus industry’s possible vectors of development and more effectively confront future threats. You, too, can learn what actions various malicious programs take in infected systems and how to withstand them.
A family of Linux Trojans. One of its representatives is described below.
A modified version of Linux.DDoS.87 and Linux.DDoS.89. Its main differences from Linux.DDoS.89 are as follows:
The Trojan’s configuration looks as follows:
Number | Value | Purpose |
---|---|---|
3 | listening tun0 | main output to stdin |
4 | Host | Command and control (C&C) server’s IP address |
5 | Port | C&C server’s port |
6 | "https://youtube.com/watch?v=dQw4w9WgXcQ" | |
7 | "/proc/" | runkiller |
8 | "/exe" | runkiller |
9 | " (deleted)" | |
10 | "/fd" | runkiller |
11 | ".anime" | runkiller |
12 | "REPORT %s:%s" | runkiller |
13 | "HTTPFLOOD" | runkiller |
14 | "LOLNOGTFO" | runkiller |
15 | "\x58\x4D\x4E\x4E\x43\x50\x46\x22" | runkiller |
16 | "zollard" | runkiller |
17 | "GETLOCALIP" | |
18 | Host | |
19 | Port | |
20 | "shell" | |
21 | "enable" | |
22 | "system" | |
23 | "sh" | |
24 | "/bin/busybox MIRAI" | |
25 | "MIRAI: applet not found" | |
26 | "ncorrect" | |
27 | "/bin/busybox ps" | |
28 | "/bin/busybox kill -9 " | |
29 | "TSource Engine Query" | |
30 | "/etc/resolv.conf" | |
31 | "nameserver" | |
32 | "Connection: keep-alive" | |
33 | "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8" | |
34 | "Accept-Language: en-US,en;q=0.8" | |
35 | "Content-Type: application/x-www-form-urlencoded" | |
36 | "setCookie('" | |
37 | "refresh:" | |
38 | "location:" | |
39 | "set-cookie:" | |
40 | "content-length:" | |
41 | "transfer-encoding:" | |
42 | "chunked" | |
43 | "keep-alive" | |
44 | "connection:" | |
45 | "server: dosarrest" | |
46 | "server: cloudflare-nginx" | |
47 | "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36" | User Agent |
48 | "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36" | User Agent |
49 | "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36" | User Agent |
50 | "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36" | User Agent |
51 | "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7" | User Agent |
All samples of the Trojan use a function that hides the following strings:
def decode(str_enc):
return "".join([chr(ord(x) ^ 0x22) for x in str_enc])
Once launched, the Trojan removes its executable file from the disk, blocks the SIGINT signal with the help of sigprocmask, and sets the parameter SIG_IGN for SIGCHLD and a handler for SIGTRAP.
Then the Trojan tries to open the /dev/watchdog file for reading/writing (/dev/misc/watchdog is also checked) and, if successful, disables the watchdog timer.
ioctl(fd, WDIOC_SETOPTION, WDIOS_DISABLECARD)
The Trojan subsequently opens a root folder and sends a request to the address 8.8.8.8:53 to get the IP address of its network traffic.
Next, the Trojan calculates a function taken from the argv[0] value:
def check(name):
print name
a = [ord(x) for x in name]
sum = (0 - 0x51) & 0xff
for i in [2,4,6,8,10,12]:
z = (~a[i % len(a)] & 0xff)
sum = (sum + z)&0xff
#print "%x %x %x" % (z, sum, sum % 9)
return sum % 9
This function returns a number from 0 to 8 that represents an index in a function array:
off_8055DC0 dd offset bind_socket ; DATA XREF: main+109o
.rodata:08055DC4 dd offset sub_80517E0
.rodata:08055DC8 dd offset sub_8051730
.rodata:08055DCC dd offset create_config
.rodata:08055DD0 dd offset sub_8051760
.rodata:08055DD4 dd offset sub_80523F0
.rodata:08055DD8 dd offset strcopy
.rodata:08055DDC dd offset runkiller
.rodata:08055DE0 dd offset sub_804E900
If argv[0] == “./dvrHelper”, a parental process receives the SIGTRAP signal (for which a handler was previously installed). The handler, in turn, modifies the IP address taken from the configuration and the C&C server’s port to which the Trojan will connect.
Then a listening socket is opened at the address 127.0.0.1:48101. If this port is busy with another process, the Trojan runs a function that finds the process and kills it.
The Trojan subsequently generates a name that looks like a random sequence containing the characters [a-z 0-9] and writes it to argv[0]. Using the prctl function, the process’s name is changed to a random one.
Next, the Trojan creates child processes and terminates the parental one. All further steps are performed in a child process—in particular, a structure containing handlers is filled in. Then a function responsible for scanning telnet nodes and a function that terminates the processes of other Trojans are launched. The Trojan then runs a handler for incoming instructions sent from the C&C server. If the Trojan detects that a connection to a local server is being established, it runs a child process to scan vulnerable telnet nodes and terminates the parental process.
The picture below shows a code fragment for Linux.DDoS.87 (left column) and Linux.Mirai (right column).
Linux.Mirai.4394
Linux.Mirai.4790
Linux.Mirai.4797
Linux.Mirai.4798
Linux.Mirai.4799
Linux.Mirai.4815
Linux.Mirai.4818
Linux.Mirai.4852
Linux.Mirai.4892
Linux.Mirai.4895
Linux.Mirai.4897
Linux.Mirai.4904
Linux.Mirai.4905
Linux.Mirai.4906
Linux.Mirai.4907
Linux.Mirai.4925
Linux.Mirai.4943
Linux.Mirai.4947
Linux.Mirai.4948
Linux.Mirai.4949
Linux.Mirai.4950
Linux.Mirai.4951
Linux.Mirai.4952
Linux.Mirai.4953
Linux.Mirai.4955
Linux.Mirai.4956
Linux.Mirai.4957
Linux.Mirai.4966
Linux.Mirai.4967
Linux.Mirai.4968
Linux.Mirai.4969
Linux.Mirai.4970
Linux.Mirai.4971
Linux.Mirai.4972
Linux.Mirai.4973
Linux.Mirai.4975
Linux.Mirai.4984
Linux.Mirai.4989
Linux.Mirai.4990
Linux.Mirai.4992
Linux.Mirai.4993
Linux.Mirai.5000
Linux.Mirai.5001
Linux.Mirai.5002
Linux.Mirai.5003
Linux.Mirai.5004
Linux.Mirai.5005
Linux.Mirai.5006
Linux.Mirai.5007
Linux.Mirai.5008
According to statistics, every fifth program for Android contains a vulnerability (or, in other words, a "loophole") that lets cybercriminals successfully introduce Trojans onto mobile devices and manipulate them into doing whatever actions they need them to.
Dr.Web Security Auditor for Android diagnoses and analyses a mobile device’s security and offers solutions to address security problems and vulnerabilities.