A #letter4u campaign photo tweeted on the Supreme Leader's Twitter account.

On January 21, during the aftermath of the Charlie Hebdo attacks in France,  Iran's Supreme Leader Ayatollah  Seyyed Ali Khamenei penned an open letter to the ‘youth in Europe and North America’ defending Islam, and the Western world's skewed reception of the religion. He also started tweeting the sentiments of the letter on his @khamenei_ir twitter account, starting the hashtag #Letter4U. A closer look of this hashtag indicates it remains active through bots, which are still crawling through Twitter four months after the launch of the campaign.

Don’t allow the arrogants to hypocritically introduce their own recruited terrorists as representatives of Islam. #ISIS #BokoHaram #Letter4U

— Khamenei.ir (@khamenei_ir) January 21, 2015

In late March Morgan Carlston noted that spam bots were promoting the hashtag on Twitter.

well this is friggin creepy. #pro-#iran hackers seem to have been busy on @twitter… #IranTalks #nuclear pic.twitter.com/921cSU3NNx — Morgan Carlston (@MorganCarlston) March 22, 2015

Morgan elaborated in a blog post:

There are hundreds if not thousands of accounts, most of them with over 10000 tweets. Twitter has a limit of 1000 tweets per day, and the accounts seem to have been created with this in mind.
Many of the accounts use fake photos taken from a variety of places. Some of them show celebrities, while others journalists or other media personalities.

.@AnnaLindow thought you should be aware of this: someone using your photo and spreading pro-#Iran govt propaganda pic.twitter.com/CzqlZAJY97

— Morgan Carlston (@MorganCarlston) March 22, 2015

David Masad, a computational science researcher retrieved the tweet rhythm for the hashtag between May 8th to the 11th, and found the image below, which indicates that bots are still being deployed to spread tweets with the #letter4u hashtag, along with a link to Khamenei's website. Mason explained in an email to Global Voices,

The chart shows the exact same number of tweets using the hashtag being tweeted at precise, regular intervals, with no changes based on the time of day. Human conversations go in bursts, exhibit cycles based on times of day that people are in Twitter, and in general are *not* regular.

The tweet frequency for #letter4u from May 8th to 11th. Image provided by David Mason, and used with permission.