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How to protect yourself from Ransomware WannaCry

by | Tutorials

Earlier today, our customers detected a large number of ransomware attacks around the world. In these attacks, data is encrypted with the extension “.WCRY” added to the filenames.

Our analysis indicates the attack, dubbed “WannaCry”, is initiated through an SMBv2 remote code execution in Microsoft Windows. This exploit (codenamed “EternalBlue”) has been made available on the internet through the Shadowbrokers dump on April 14th, 2017 and patched by Microsoft on March 14.

So we strongly recommend to carefully the following notes thoroughly:

  • Be careful to click on harmful links in your emails.
  • Be wary of visiting unsafe or unreliable sites.
  • Never click on a link that you do not trust on a web page or access to Facebook or messaging applications such as WatSab and other applications.
  • If you receive a message from your friend with a link, ask him before opening the link to confirm, (infected machines send random messages with links).
  • Keep your files backed up regularly and periodically: Realtime – Online – Offline.
  • Be aware of fraudulent e-mail messages that use names similar to popular services such as PayePal instead of PayPal or use popular service names without commas or excessive characters.
  • Use anti virus and always be updated.
  • Use Windows Update to update windows to close the gap.
  • Close port 139, 445, 3389
  • Disable SMB Services
  • Update all of your system to the latest version
  • Deny IP of C&C Ransomware Server on IDS-IPS-Firewall…
  • Update or backup your data to Dropbox, Owncloud, Google Drive …

WannaCryWannaDecrypt0r NSA-Cybereweapon-Powered Ransomware Worm

  • Virus Name: WannaCrypt, WannaCry, WanaCrypt0r, WCrypt, WCRY
  • Vector: All Windows versions before Windows 10 are vulnerable if not patched for MS-17-010. It uses EternalBlue MS17-010 to propagate.
  • Ransom: between $300 to $600. There is code to ‘rm’ (delete) files in the virus. Seems to reset if the virus crashes.
  • Backdooring: The worm loops through every RDP session on a system to run the ransomware as that user. It also installs the DOUBLEPULSAR backdoor. It corrupts shadow volumes to make recovery harder. (source: malwarebytes)
  • Kill switch: If the website www.iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com is up the virus exits instead of infecting the host. (source: malwarebytes). This domain has been sinkholed, stopping the spread of the worm.

SECURITY BULLETIN AND UPDATES HERE: https://technet.microsoft.com/en-us/library/security/ms17-010.aspx

Microsoft first patch for XP since 2017: https://blogs.technet.microsoft.com/msrc/2017/05/12/customer-guidance-for-wannacrypt-attacks/

Killswitch source: https://blog.malwarebytes.com/threat-analysis/2017/05/the-worm-that-spreads-wanacrypt0r/

Infections

Malware samples

Binary blob in PE crypted with pass ‘WNcry@2ol7’, credits to ens!

Informative Tweets

Cryptography details

  • encrypted via AES-128-CBC (custom implementation in the binary)
  • AES key generated with a CSPRNG, CryptGenRandom
  • AES key is encrypted by RSA-2048 (windows RSA implementation)
  • https://haxx.in/key1.bin (the ransomware pubkey, used to encrypt the aes keys)
  • https://haxx.in/key2.bin (the dll decryption privkey) the CryptImportKey() rsa key blob dumped from the DLL by blasty.

Bitcoin ransom addresses

3 addresses hard coded into the malware.

C&C centers

  • gx7ekbenv2riucmf.onion
  • 57g7spgrzlojinas.onion
  • xxlvbrloxvriy2c5.onion
  • 76jdd2ir2embyv47.onion
  • cwwnhwhlz52maqm7.onion

Languages

All language ransom messages available here: https://transfer.sh/y6qco/WANNACRYDECRYPTOR-Ransomware-Messages-all-langs.zip

m_bulgarian, m_chinese (simplified), m_chinese (traditional), m_croatian, m_czech, m_danish, m_dutch, m_english, m_filipino, m_finnish, m_french, m_german, m_greek, m_indonesian, m_italian, m_japanese, m_korean, m_latvian, m_norwegian, m_polish, m_portuguese, m_romanian, m_russian, m_slovak, m_spanish, m_swedish, m_turkish, m_vietnamese

File types

The filetypes it looks for to encrypt are

.doc, .docx, .xls, .xlsx, .ppt, .pptx, .pst, .ost, .msg, .eml, .vsd, .vsdx, .txt, .csv, .rtf, .123, .wks, .wk1, .pdf, .dwg, .onetoc2, .snt, .jpeg, .jpg, .docb, .docm, .dot, .dotm, .dotx, .xlsm, .xlsb, .xlw, .xlt, .xlm, .xlc, .xltx, .xltm, .pptm, .pot, .pps, .ppsm, .ppsx, .ppam, .potx, .potm, .edb, .hwp, .602, .sxi, .sti, .sldx, .sldm, .sldm, .vdi, .vmdk, .vmx, .gpg, .aes, .ARC, .PAQ, .bz2, .tbk, .bak, .tar, .tgz, .gz, .7z, .rar, .zip, .backup, .iso, .vcd, .bmp, .png, .gif, .raw, .cgm, .tif, .tiff, .nef, .psd, .ai, .svg, .djvu, .m4u, .m3u, .mid, .wma, .flv, .3g2, .mkv, .3gp, .mp4, .mov, .avi, .asf, .mpeg, .vob, .mpg, .wmv, .fla, .swf, .wav, .mp3, .sh, .class, .jar, .java, .rb, .asp, .php, .jsp, .brd, .sch, .dch, .dip, .pl, .vb, .vbs, .ps1, .bat, .cmd, .js, .asm, .h, .pas, .cpp, .c, .cs, .suo, .sln, .ldf, .mdf, .ibd, .myi, .myd, .frm, .odb, .dbf, .db, .mdb, .accdb, .sql, .sqlitedb, .sqlite3, .asc, .lay6, .lay, .mml, .sxm, .otg, .odg, .uop, .std, .sxd, .otp, .odp, .wb2, .slk, .dif, .stc, .sxc, .ots, .ods, .3dm, .max, .3ds, .uot, .stw, .sxw, .ott, .odt, .pem, .p12, .csr, .crt, .key, .pfx, .der

credit herulume, thanks for extracting this list from the binary.

Some other interesting strings

BAYEGANSRV\administrator Smile465666SA wanna18@hotmail.com

credit: nulldot https://pastebin.com/0LrH05y2

Encrypted file format

<64-bit SIGNATURE>        - WANACRY!
 - 256 for 2048-bit keys, cannot exceed 4096-bits
           - 256 bytes if keys are 2048-bits
<32-bit value>            - unknown
<64 bit file size>        - return by GetFileSizeEx
          - with custom AES-128 in CBC mode

credit for reversing this file format info: cyg_x11

Vulnerability disclosure

The specific vulnerability that it uses to propagate is ETERNALBLUE.

This was developed by “equation group” an exploit developer group associated with the NSA and leaked to the public by “the shadow brokers”. Microsoft fixed this vulnerability March 14, 2017. They were not 0 days at the time of release.