“Salad Words” Spam Run Exploits Unlikely Resources

We recently reported about a large spike of commercial spam that employed micro-sized salad words or random gibberish words found in the email body to bypass spam filters. The content of these messages varied from hair loss cures to car sales to retailer coupons. Most of the samples contained links to websites they themselves advertise.

Aside from the tactic used, this particular spam run is notable because its two primary sources are hosting services providers and newly-registered domains that were not previously associated with known or detected spam activity. Service providers are often considered trustworthy but it now seems that they are being openly abused by spammers.

New Spam Sources

Majority of the spam-sending IPs were sourced from a company associated with a Canadian hosting service provider. The remaining IP addresses belong to US-based providers.

Newly-registered domains were another noteworthy spam source. Spammers created these newly-born domains and wasted no time in using these new domains as the sender address and URL inside the mail body, as seen in the table below. They started spamming only minutes after registering the new domains. When unsuspecting users clicked these domains found in the email message, they are redirected to spam websites.

Spammers may have used new domains with no spam history because these may not arouse suspicion. Analysis from our engineers shows that all the domains were filed under the same registrar by one organization.

Figure 1. Time between domain registration and first known spamming activity

Figure 2 shows the peak spam volume associated with this campaign within a 24-hour period. Closer inspection reveals that the spam run was composed of multiple short burst of spamming activity, shown in Figure 3. Each burst came from one IP address, followed by another burst from another IP address, and so on. Such behavior is most likely an attempt to evade IP-based filtering solutions.

Figure 2. Peak spam volume within specific hours

Figure 3. Multiple IPs contribute to the spam runs

Based on our IP statistics, 85% of the affected victims came from the US. Other top affected countries include Germany, Canada, Great Britain, and New Zealand.

Countermeasures

As spam techniques continue to adapt and evolve, users are advised to be on guard when opening their emails. Never open messages, download attachments and click links from unknown senders. Security solutions, such as spam filtering, can help protect users from such threats.

Post from: Trendlabs Security Intelligence Blog – by Trend Micro

“Salad Words” Spam Run Exploits Unlikely Resources