Trustwave SpiderLabs Exposes Unique Cybersecurity Threats in the Public Sector. Learn More

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SpiderLabs Blog

Locky Part 2: As the Seasons Change so is Locky

It's that time of year when the seasons are changing. The Northern Hemisphere moves into Autumn, and the Southern Hemisphere moves to Spring. So it is with Locky. As we discussed in our last post, spam campaigns were downloading Locky ransomware that used ".lukitus" as the encrypted file extension name. Now Necurs botnet is back spamming out Locky again, only this time with a different file extension name.

Our Spam Research Database shows the spikes of emails coming from the Necurs botnet on Sept 19, 2017.

BSL_12449_ea69c0ea-8e12-4ea9-9f1d-302d03b795f7

 

The table below shows the top 10 countries where Necurs spam originates from. These numbers indicate machines compromised with Necurs:

8540_2e8056de-c9b7-46d3-88c7-38912c6d69d6

 

Samples of the email messages are shown below. They come with two different subject lines:

8743_37bbdfa9-8da5-43d1-ab5f-99a57a9ce683

 

These messages come with .7zip attachments that contains .vbs files:

7653_0223a6fc-fd62-4c44-8974-1ac87c188c4b

Examining the .vbs code closely, you can find the URLs that are accessed once the .vbs file is executed. The image below shows a code snippet of the URLs

BSL_11202_ae204893-fb11-4d34-a54f-854c44328054

 

Accessing these URLs, can download the Locky ransomware executable files:

  • www[.]elitecommunications.co[.]uk/87thiuh3gfDGS?
  • miliaraic[.]ru/p66/87thiuh3gfDGS
  • troyriser[.]com/87thiuh3gfDGS?
  • dmlex[.]adlino[.]be/DKndhFG72?
  • targeter[.]su/p66/DKndhFG72
  • cornyproposal[.]com/DKndhFG72?

Below are images for URL requests and responses respectively:

8781_39c48752-baf1-48ee-ac02-8a07958e7a3d

8781_39c48752-baf1-48ee-ac02-8a07958e7a3d

 

Downloaded executable files (metadata):

MD5: cd2e485d86bd2598a8728f81a54ba774
SHA1: 9ec96c64691d1c7988cba48d5c140d4c2f2db8f8
SIZE: 649,216 bytes

MD5: bab1c043a2fba947f682b6a012a9f362
SHA1: 4709c02b59f0b20c45e798e62a00b3914f738403
SIZE: 660,480

After the .vbs script finishes downloading the executable file, it will automatically execute the ransomware, which, as expected, it encrypts your files. Note that the file extension has been changed to ".ykcol" which is Locky spelled backwards:

8514_2d560dc1-20f4-4014-8033-985bb9a4830a

 

List of file extensions that this variant will encrypt:

BSL_12466_eb020596-1eca-404d-80d6-02ab98ee0268

 

Locky ransom notes in various formats:

Image File (ykcol.bmp):
11481_bb3c17f2-0661-4ca0-9957-d9b660c751b6

 

HTML File (ykcol.htm)8537_2e7b0678-d905-4e1f-bdc5-abbfde2f06ef

 

Added Registry to change wallpaper into the ransom note.9943_736c4a5c-57ad-4bdd-b3ce-ef9f30bdf8ab

 

Finally, the image below shows the Locky decryptor site. The victim needs to use a TOR browser to access the URL provided in the ransom note:8749_37d5094b-9fdf-4ec6-b142-df97bfb53a71

Asking for 0.25 BTC or USD 1000

 

Indicators of Compromise (IoCs)

VBS Downloaders:

  • f8d91dde125cb5b1b4c336d1d5a7d9e1b444637f
  • e4976b8e04cf93450286b91eebd6eecb79361c76

Locky Ransomware:

  • 9ec96c64691d1c7988cba48d5c140d4c2f2db8f8
  • 4709c02b59f0b20c45e798e62a00b3914f738403

 

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