Modern technologies have enabled illicit firearms trafficking to partially merge with cybercrime, while also allowing its off-line aspects to become increasingly complex. The online trade of firearms, their components, 3D blueprints and illicit substances carried out by criminals on both the surface Web and dark Web is increasingly difficult to address as a consequence of the exponential growth in the amount of information disseminated on the Internet. On the other hand, law enforcement agencies are confronted with significant challenges that require the development of sophisticated technological solutions capable of processing large volumes of data, identifying relevant information in a timely manner and creating networks of connections between potential criminal groups. This article presents a real-world practical system, namely the CEASEFIRE one, powered by advanced artificial intelligence technologies that can assist law enforcement personnel in addressing the above described challenges.

Automated visual firearms classification from RGB images is an important real-world task with applications in public space security, intelligence gathering and law enforcement investigations. When applied to images massively crawled from the World Wide Web (including social media and dark Web sites), it can serve as an important component of systems that attempt to identify criminal firearms trafficking networks, by analyzing Big Data from open-source intelligence. Deep Neural Networks (DNN) are the state-of-the-art methodology for achieving this, with Convolutional Neural Networks (CNN) being typically employed. The common transfer learning approach consists of pretraining on a large-scale, generic annotated dataset for whole-image classification, such as ImageNet-1k, and then finetuning the DNN on a smaller, annotated, task-specific, downstream dataset for visual firearms classification. Neither Visual Transformer (ViT) neural architectures nor Self-Supervised Learning (SSL) approaches have been so far evaluated on this critical task. SSL essentially consists of replacing the traditional supervised pretraining objective with an unsupervised pretext task that does not require ground-truth labels. This paper evaluates a common CNN and a typical ViT architecture in combination with different SSL methods, comparing them against each other and against supervised pretraining in terms of downstream classification accuracy. Additionally, “CrawledFirearmsRGB” is introduced as a new, challenging image dataset for visual classification of firearms and other concepts related to on-line criminal networks. Finally, a new mixed pretraining objective is formulated that combines SSL and whole-image classification, under a multitask learning setting. The experimental results, indicate the superiority of certain SSL pretraining methods that cooperate well with the ViT architecture, even when the pretraining dataset is of a scale similar or identical to that of CrawledFirearmsRGB, despite the fact that no ground-truth labels are exploited.

Automated detection of contraband items in X-ray images can significantly increase public safety, by enhancing the productivity and alleviating the mental load of security officers in airports, subways, customs/post offices, etc. The large volume and high throughput of passengers, mailed parcels, etc., during rush hours practically make it a Big Data problem. Modern computer vision algorithms relying on Deep Neural Networks (DNNs) have proven capable of undertaking this task even under resource-constrained and embedded execution scenarios, e.g., as is the case with fast, single-stage object detectors. However, no comparative experimental assessment of the various relevant DNN components/methods has been performed under a common evaluation protocol, which means that reliable cross-method comparisons are missing. This paper presents exactly such a comparative assessment, utilizing a public relevant dataset and a well-defined methodology for selecting the specific DNN components/modules that are being evaluated. The results indicate the superiority of Transformer detectors, the obsolete nature of auxiliary neural modules that have been developed in the past few years for security applications and the efficiency of the CSP-DarkNet backbone CNN.

State-of-the-art deep neural unsupervised video summarization methods mostly fall under the adversarial reconstruction framework. This employs a Generative Adversarial Network (GAN) structure and Long Short-Term Memory (LSTM) autoencoders during its training stage. The typical result is a selector LSTM that sequentially receives video frame representations and outputs corresponding scalar importance factors, which are then used to select key-frames. This basic approach has been augmented with an additional Deep Reinforcement Learning (DRL) agent, trained using the Discriminator’s output as a reward, which learns to optimize the selector’s outputs. However, local minima are a well-known problem in DRL. Thus, this paper presents a novel regularizer for escaping local loss minima, in order to improve unsupervised key-frame extraction. It is an additive loss term employed during a second training phase, that rewards the difference of the neural agent’s parameters from those of a previously found good solution. Thus, it encourages the training process to explore more aggressively the parameter space in order to discover a better local loss minimum. Evaluation performed on two public datasets shows considerable increases over the baseline and against the state-of-the-art.