GandCrab Ransomware Distribution Begins in Korea

A new ransomware named GandCrab is also being distributed in Korea. The ransomware infects PC when user visits a website vulnerable due to exploit kit. Ever since its first discovery, GandCrab has been distributed incessantly across the cyber sphere.

Once PC is infected by GandCrab ransomware, file extension is changed to .GDCB and GDCB-DECRYPT.txt is created.

Figure 1. Extension change due to the ransomware

When GandCrab ransomware is executed, it copies itself as ‘%appdata%\Microsoft\[Randomstr{6}].exe’ adds to registry so it can remain in PC and secure its persistence for execution.

File creation path  %appdata%\Microsoft\[Randomstr{6}].exe
 Registry HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
Table 1. Copying file and registering auto run for a continuous execution

Afterward, it checks if a certain process is running and if so, it terminates that process.

Process termination target 
msftesql.exe
sqlagent.exe
sqlbrowser.exe
sqlservr.exe
sqlwriter.exe
oracle.exe
ocssd.exe
dbsnmp.exe
synctime.exe
mydesktopqos.exe
agntsvc.exeisqlplussvc.exe
xfssvccon.exe
mydesktopservice.exe
ocautoupds.exe
agntsvc.exeagntsvc.exe
agntsvc.exeencsvc.exe
firefoxconfig.exe
tbirdconfig.exe
ocomm.exe
mysqld.exe
mysqld-nt.exe
mysqld-opt.exe
dbeng50.exe
sqbcoreservice.exe
excel.exe
infopath.exe
msaccess.exe
mspub.exe
onenote.exe
outlook.exe
powerpnt.exe
steam.exe
thebat.exe
thebat64.exe
thunderbird.exe
visio.exe
winword.exe
wordpad.exe
Table 2. Process termination target list

The ransomware also collects and transfers user information by C2 connection. It checks the list of running process among collected user information and sends the list in case AV software is in use. The list of processes that are checked is as below.

List of anti-malware that are checked if in use
AVP.EXE
ekrn.exe
avgnt.exe
ashDisp.exe
NortonAntiBot.exe
Mcshield.exe
avengine.exe
cmdagent.exe
smc.exe
persfw.exe
pccpfw.exe
fsguiexe.exe
cfp.exe
msmpeng.exe
Table 3. Anti-malware software that are checked if in use

Other than that, the malware also sends IP, PC_USER, PC_NAME, PC_GROUP, Language, OS version, OS bit, Identifier, and Storage Device information to C2 server.

C2 domain 
no****ra***m.bit
em***o*t.bit
ga****ab.bit
Table 4. C2 domain

Next, it proceeds with encryption. The targets are:

Encryption target extensions (456 total)
.1cd, .3dm, .3ds, .3fr, .3g2, .3gp, .3pr, .7z, .7zip, .aac, .ab4, .abd, .acc, .accdb, .accde, .accdr, .accdt, .ach, .acr, .act, .adb, .adp, .ads, .agdl, .ai, .aiff, .ait, .al, .aoi, .apj, .apk, .arw, .ascx, .asf, .asm, .asp, .aspx, .asset, .asx, .atb, .avi, .awg, .back, .backup, .backupdb, .bak, .bank, .bay, .bdb, .bgt, .bik, .bin, .bkp, .blend, .bmp, .bpw, .bsa, .c, .cash, .cdb, .cdf, .cdr, .cdr3, .cdr4, .cdr5, .cdr6, .cdrw, .cdx, .ce1, .ce2, .cer, .cfg, .cfn, .cgm, .cib, .class, .cls, .cmt, .config, .contact, .cpi, .cpp, .cr2, .craw, .crt, .crw, .cry, .cs, .csh, .csl, .css, .csv, .d3dbsp, .dac, .das, .dat, .db, .db_journal, .db3, .dbf, .dbx, .dc2, .dcr, .dcs, .ddd, .ddoc, .ddrw, .dds, .def, .der, .des, .design, .dgc, .dgn, .dit, .djvu, .dng, .doc, .docm, .docx, .dot, .dotm, .dotx, .drf, .drw, .dtd, .dwg, .dxb, .dxf, .dxg, .edb, .eml, .eps, .erbsql, .erf, .exf, .fdb, .ffd, .fff, .fh, .fhd, .fla, .flac, .flb, .flf, .flv, .flvv, .forge, .fpx, .fxg, .gbr, .gho, .gif, .gray, .grey, .groups, .gry, .h, .hbk, .hdd, .hpp, .html, .ibank, .ibd, .ibz, .idx, .iif, .iiq, .incpas, .indd, .info, .info_, .ini, .iwi, .jar, .java, .jnt, .jpe, .jpeg, .jpg, .js, .json, .k2p, .kc2, .kdbx, .kdc, .key, .kpdx, .kwm, .laccdb, .lbf, .lck, .ldf, .lit, .litemod, .litesql, .lock, .log, .ltx, .lua, .m, .m2ts, .m3u, .m4a, .m4p, .m4v, .ma, .mab, .mapimail, .max, .mbx, .md, .mdb, .mdc, .mdf, .mef, .mfw, .mid, .mkv, .mlb, .mmw, .mny, .money, .moneywell, .mos, .mov, .mp3, .mp4, .mpeg, .mpg, .mrw, .msf, .msg, .myd, .nd, .ndd, .ndf, .nef, .nk2, .nop, .nrw, .ns2, .ns3, .ns4, .nsd, .nsf, .nsg, .nsh, .nvram, .nwb, .nx2, .nxl, .nyf, .oab, .obj, .odb, .odc, .odf, .odg, .odm, .odp, .ods, .odt, .ogg, .oil, .omg, .one, .orf, .ost, .otg, .oth, .otp, .ots, .ott, .p12, .p7b, .p7c, .pab, .pages, .pas, .pat, .pbf, .pcd, .pct, .pdb, .pdd, .pdf, .pef, .pem, .pfx, .php, .pif, .pl, .plc, .plus_muhd, .pm!, .pm, .pmi, .pmj, .pml, .pmm, .pmo, .pmr, .pnc, .pnd, .png, .pnx, .pot, .potm, .potx, .ppam, .pps, .ppsm, .ppsx,.ppt, .pptm, .pptx, .prf, .private, .ps, .psafe3, .psd, .pspimage, .pst, .ptx, .pub, .pwm, .py, .qba, .qbb, .qbm, .qbr, .qbw, .qbx, .qby, .qcow, .qcow2, .qed, .qtb, .r3d, .raf, .rar, .rat, .raw, .rdb, .re4, .rm, .rtf, .rvt, .rw2, .rwl, .rwz, .s3db, .safe, .sas7bdat, .sav, .save, .say, .sd0, .sda, .sdb, .sdf, .sh, .sldm, .sldx, .slm, .sql, .sqlite, .sqlite3, .sqlitedb, .sqlite-shm, .sqlite-wal, .sr2, .srb, .srf, .srs, .srt, .srw, .st4, .st5, .st6, .st7, .st8, .stc, .std, .sti, .stl, .stm, .stw, .stx, .svg, .swf, .sxc, .sxd, .sxg, .sxi, .sxm, .sxw, .tax, .tbb, .tbk, .tbn, .tex, .tga, .thm, .tif, .tiff, .tlg, .tlx, .txt, .upk, .usr, .vbox, .vdi, .vhd, .vhdx, .vmdk, .vmsd, .vmx, .vmxf, .vob, .vpd, .vsd, .wab, .wad, .wallet, .war, .wav, .wb2, .wma, .wmf, .wmv, .wpd, .wps, .x11, .x3f, .xis, .xla, .xlam, .xlk, .xlm, .xlr, .xls, .xlsb, .xlsm, .xlsx, .xlt, .xltm, .xltx, .xlw, .xml, .xps, .xxx, .ycbcra, .yuv, .zip
Table 5. Encryption target extensions

Some paths and filenames are excluded from encryption targets..

Paths excluded from encryption target list  Files excluded from encryption target list
\ProgramData\
\Program Files\
\Tor Browser\
\Ransomware\
\All Users\
\Local Settings\
%ProgramFiles%
%CommonProgramFiles%
%windir%
%LOCALAPPDATA%
desktop.ini
autorun.inf
ntuser.dat
iconcache.db
bootsect.bak
boot.ini
ntuser.dat.log
thumbs.db
GDCB-DECRYPT.txt
Table 6. Targets excluded from encryption list

After encryption is completed, it deletes Volumn Shadow Copy using wmic, vassadmin and etc to prevent restoration.

Figure 2. Ransom note

Although it is not possible to completely prevent infection or restore the system, updating Windows security patch and V3 to the latest version is required to minimize the damage.

Users should be vigilant with executing email attachments from unreliable source of accessing unidentified webpage. Also, flash security update should conducted as operators exploit flash vulnerabilities.

AhnLab V3 detects GandCrab ransomware under the following aliases:

[File Detection]

Trojan/Win32.GandCrypt(2018.02.05.07)

[Behavior Detection]

Malware/MDP.Ransom.M1171

Categories:Malware Information

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